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  • richardmitnick 9:17 am on May 26, 2021 Permalink | Reply
    Tags: "Materials breakthrough enables twistronics for bulk systems", "Twistronics" is the study of how the angle between layers of two-dimensional materials can change their electrical properties., A new way to control light emission from materials., , , , Optics, The breakthrough by SMART researchers offers a new approach to tune the optical properties of technologically relevant materials by changing the twist angle between stacked films at room temperature., The research can also be meaningful for developing the fundamental physics in the field of "twistronics."   

    From MIT : “Materials breakthrough enables twistronics for bulk systems” 

    MIT News

    From MIT

    May 24, 2021
    Singapore-MIT Alliance for Research and Technology

    1
    SMART researchers have found that phenomena related to the formation of moiré superlattices observed in two-dimensional systems can be translated to tune optical properties of three-dimensional, bulk-like hexagonal boron nitride, even at room temperature. Credit: Singapore-MIT Alliance for Research and Technology.

    Researchers from the Low Energy Electronic Systems (LEES) interdisciplinary research group at the Singapore-MIT Alliance for Research and Technology (SMART), MIT’s research enterprise in Singapore, together with MIT and National University of Singapore [新加坡国立大学 ] (SG), have discovered a new way to control light emission from materials.

    Controlling the properties of materials has been the driving force behind many modern technologies — from solar panels to computers, smart vehicles, and lifesaving hospital equipment. But materials properties have traditionally been adjusted based on their composition, structure, and sometimes size, and most practical devices that produce or generate light use layers of materials of different compositions that can often be difficult to grow.

    The breakthrough by SMART researchers and their collaborators offers a new paradigm-shifting approach to tune the optical properties of technologically relevant materials by changing the twist angle between stacked films, at room temperature. Their findings could have a huge impact on various applications in the medical, biological, and quantum information fields. The team explain their research in a paper published recently in Nano Letters.

    “A number of new physical phenomena — such as unconventional superconductivity — have been discovered recently by stacking individual layers of atomically-thin materials on top of each other at a twist angle, which results in the formation of what we call moiré superlattices,” says corresponding author of the paper Professor Silvija Gradecak from the Department of Materials Science and Engineering at NUS and principal investigator at SMART LEES. “The existing methods focus on stacking only thin individual monolayers of film, which is laborious, while our discovery would be applicable to thick films as well — making the process of materials discovery much more efficient.”

    Their research can also be meaningful for developing the fundamental physics in the field of “twistronics” — the study of how the angle between layers of two-dimensional materials can change their electrical properties. Gradecak points out the field has so far focused on stacking individual monolayers, which requires careful exfoliation and may suffer from relaxation from a twisted state, thus limiting their practical applications. The team’s discovery could make this groundbreaking twist-related phenomenon applicable to thick film systems as well, which are easy to manipulate and industrially relevant.

    “Our experiments showed that the same phenomena leading to formation of moiré superlattices in two-dimensional systems can be translated to tune optical properties of three-dimensional, bulk-like hexagonal boron nitride (hBN), even at room temperature,” says Hae Yeon Lee, the lead author of the paper and a materials science and engineering PhD candidate at MIT. “We found that both the intensity and color of stacked, thick hBN films can be continuously tuned by their relative twist angles and intensity increased by more than 40 times.”

    The research results open up a new way to control optical properties of thin films beyond the conventionally used structures, especially for applications in medicine and environmental or information technologies.

    The research is carried out by SMART and supported by the National Research Foundation (NRF) Singapore under its Campus for Research Excellence And Technological Enterprise (CREATE) program.

    LEES is creating new integrated circuit technologies that result in increased functionality, lower power consumption, and higher performance for electronic systems. These integrated circuits of the future will impact applications in wireless communications and power electronics, LED lighting, and displays. LEES has a vertically-integrated research team possessing expertise in materials, devices, and circuits, comprising multiple individuals with professional experience within the semiconductor industry. This ensures that the research is targeted to meet the needs of the semiconductor industry both within Singapore and globally.

    SMART was established by MIT in partnership with the NRF in 2007. SMART is the first entity in CREATE. SMART serves as an intellectual and innovation hub for cutting-edge research projects in areas of interest to both Singapore and MIT. It currently comprises an Innovation Center and five interdisciplinary research group: Antimicrobial Resistance, Critical Analytics for Manufacturing Personalized-Medicine, Disruptive and Sustainable Technologies for Agricultural Precision, Future Urban Mobility, and LEES.

    SMART research is funded by the NRF under the CREATE program.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    MIT Seal

    USPS “Forever” postage stamps celebrating Innovation at MIT.

    MIT Campus

    Massachusetts Institute of Technology (MIT)(US) is a private land-grant research university in Cambridge, Massachusetts. The institute has an urban campus that extends more than a mile (1.6 km) alongside the Charles River. The institute also encompasses a number of major off-campus facilities such as the MIT Lincoln Laboratory, the Bates Center, and the Haystack Observatory, as well as affiliated laboratories such as the Broad and Whitehead Institutes.

    Founded in 1861 in response to the increasing industrialization of the United States, MIT adopted a European polytechnic university model and stressed laboratory instruction in applied science and engineering. It has since played a key role in the development of many aspects of modern science, engineering, mathematics, and technology, and is widely known for its innovation and academic strength. It is frequently regarded as one of the most prestigious universities in the world.

    As of December 2020, 97 Nobel laureates, 26 Turing Award winners, and 8 Fields Medalists have been affiliated with MIT as alumni, faculty members, or researchers. In addition, 58 National Medal of Science recipients, 29 National Medals of Technology and Innovation recipients, 50 MacArthur Fellows, 80 Marshall Scholars, 3 Mitchell Scholars, 22 Schwarzman Scholars, 41 astronauts, and 16 Chief Scientists of the U.S. Air Force have been affiliated with MIT. The university also has a strong entrepreneurial culture and MIT alumni have founded or co-founded many notable companies. MIT is a member of the Association of American Universities (AAU).

    Foundation and vision

    In 1859, a proposal was submitted to the Massachusetts General Court to use newly filled lands in Back Bay, Boston for a “Conservatory of Art and Science”, but the proposal failed. A charter for the incorporation of the Massachusetts Institute of Technology, proposed by William Barton Rogers, was signed by John Albion Andrew, the governor of Massachusetts, on April 10, 1861.

    Rogers, a professor from the University of Virginia (US), wanted to establish an institution to address rapid scientific and technological advances. He did not wish to found a professional school, but a combination with elements of both professional and liberal education, proposing that:

    “The true and only practicable object of a polytechnic school is, as I conceive, the teaching, not of the minute details and manipulations of the arts, which can be done only in the workshop, but the inculcation of those scientific principles which form the basis and explanation of them, and along with this, a full and methodical review of all their leading processes and operations in connection with physical laws.”

    The Rogers Plan reflected the German research university model, emphasizing an independent faculty engaged in research, as well as instruction oriented around seminars and laboratories.

    Early developments

    Two days after MIT was chartered, the first battle of the Civil War broke out. After a long delay through the war years, MIT’s first classes were held in the Mercantile Building in Boston in 1865. The new institute was founded as part of the Morrill Land-Grant Colleges Act to fund institutions “to promote the liberal and practical education of the industrial classes” and was a land-grant school. In 1863 under the same act, the Commonwealth of Massachusetts founded the Massachusetts Agricultural College, which developed as the University of Massachusetts Amherst (US)). In 1866, the proceeds from land sales went toward new buildings in the Back Bay.

    MIT was informally called “Boston Tech”. The institute adopted the European polytechnic university model and emphasized laboratory instruction from an early date. Despite chronic financial problems, the institute saw growth in the last two decades of the 19th century under President Francis Amasa Walker. Programs in electrical, chemical, marine, and sanitary engineering were introduced, new buildings were built, and the size of the student body increased to more than one thousand.

    The curriculum drifted to a vocational emphasis, with less focus on theoretical science. The fledgling school still suffered from chronic financial shortages which diverted the attention of the MIT leadership. During these “Boston Tech” years, MIT faculty and alumni rebuffed Harvard University (US) president (and former MIT faculty) Charles W. Eliot’s repeated attempts to merge MIT with Harvard College’s Lawrence Scientific School. There would be at least six attempts to absorb MIT into Harvard. In its cramped Back Bay location, MIT could not afford to expand its overcrowded facilities, driving a desperate search for a new campus and funding. Eventually, the MIT Corporation approved a formal agreement to merge with Harvard, over the vehement objections of MIT faculty, students, and alumni. However, a 1917 decision by the Massachusetts Supreme Judicial Court effectively put an end to the merger scheme.

    In 1916, the MIT administration and the MIT charter crossed the Charles River on the ceremonial barge Bucentaur built for the occasion, to signify MIT’s move to a spacious new campus largely consisting of filled land on a one-mile-long (1.6 km) tract along the Cambridge side of the Charles River. The neoclassical “New Technology” campus was designed by William W. Bosworth and had been funded largely by anonymous donations from a mysterious “Mr. Smith”, starting in 1912. In January 1920, the donor was revealed to be the industrialist George Eastman of Rochester, New York, who had invented methods of film production and processing, and founded Eastman Kodak. Between 1912 and 1920, Eastman donated $20 million ($236.6 million in 2015 dollars) in cash and Kodak stock to MIT.

    Curricular reforms

    In the 1930s, President Karl Taylor Compton and Vice-President (effectively Provost) Vannevar Bush emphasized the importance of pure sciences like physics and chemistry and reduced the vocational practice required in shops and drafting studios. The Compton reforms “renewed confidence in the ability of the Institute to develop leadership in science as well as in engineering”. Unlike Ivy League schools, MIT catered more to middle-class families, and depended more on tuition than on endowments or grants for its funding. The school was elected to the Association of American Universities (US)in 1934.

    Still, as late as 1949, the Lewis Committee lamented in its report on the state of education at MIT that “the Institute is widely conceived as basically a vocational school”, a “partly unjustified” perception the committee sought to change. The report comprehensively reviewed the undergraduate curriculum, recommended offering a broader education, and warned against letting engineering and government-sponsored research detract from the sciences and humanities. The School of Humanities, Arts, and Social Sciences and the MIT Sloan School of Management were formed in 1950 to compete with the powerful Schools of Science and Engineering. Previously marginalized faculties in the areas of economics, management, political science, and linguistics emerged into cohesive and assertive departments by attracting respected professors and launching competitive graduate programs. The School of Humanities, Arts, and Social Sciences continued to develop under the successive terms of the more humanistically oriented presidents Howard W. Johnson and Jerome Wiesner between 1966 and 1980.

    MIT’s involvement in military science surged during World War II. In 1941, Vannevar Bush was appointed head of the federal Office of Scientific Research and Development and directed funding to only a select group of universities, including MIT. Engineers and scientists from across the country gathered at MIT’s Radiation Laboratory, established in 1940 to assist the British military in developing microwave radar. The work done there significantly affected both the war and subsequent research in the area. Other defense projects included gyroscope-based and other complex control systems for gunsight, bombsight, and inertial navigation under Charles Stark Draper’s Instrumentation Laboratory; the development of a digital computer for flight simulations under Project Whirlwind; and high-speed and high-altitude photography under Harold Edgerton. By the end of the war, MIT became the nation’s largest wartime R&D contractor (attracting some criticism of Bush), employing nearly 4000 in the Radiation Laboratory alone and receiving in excess of $100 million ($1.2 billion in 2015 dollars) before 1946. Work on defense projects continued even after then. Post-war government-sponsored research at MIT included SAGE and guidance systems for ballistic missiles and Project Apollo.

    These activities affected MIT profoundly. A 1949 report noted the lack of “any great slackening in the pace of life at the Institute” to match the return to peacetime, remembering the “academic tranquility of the prewar years”, though acknowledging the significant contributions of military research to the increased emphasis on graduate education and rapid growth of personnel and facilities. The faculty doubled and the graduate student body quintupled during the terms of Karl Taylor Compton, president of MIT between 1930 and 1948; James Rhyne Killian, president from 1948 to 1957; and Julius Adams Stratton, chancellor from 1952 to 1957, whose institution-building strategies shaped the expanding university. By the 1950s, MIT no longer simply benefited the industries with which it had worked for three decades, and it had developed closer working relationships with new patrons, philanthropic foundations and the federal government.

    In late 1960s and early 1970s, student and faculty activists protested against the Vietnam War and MIT’s defense research. In this period MIT’s various departments were researching helicopters, smart bombs and counterinsurgency techniques for the war in Vietnam as well as guidance systems for nuclear missiles. The Union of Concerned Scientists was founded on March 4, 1969 during a meeting of faculty members and students seeking to shift the emphasis on military research toward environmental and social problems. MIT ultimately divested itself from the Instrumentation Laboratory and moved all classified research off-campus to the MIT (US) Lincoln Laboratoryfacility in 1973 in response to the protests. The student body, faculty, and administration remained comparatively unpolarized during what was a tumultuous time for many other universities. Johnson was seen to be highly successful in leading his institution to “greater strength and unity” after these times of turmoil. However six MIT students were sentenced to prison terms at this time and some former student leaders, such as Michael Albert and George Katsiaficas, are still indignant about MIT’s role in military research and its suppression of these protests. (Richard Leacock’s film, November Actions, records some of these tumultuous events.)

    In the 1980s, there was more controversy at MIT over its involvement in SDI (space weaponry) and CBW (chemical and biological warfare) research. More recently, MIT’s research for the military has included work on robots, drones and ‘battle suits’.

    Recent history

    MIT has kept pace with and helped to advance the digital age. In addition to developing the predecessors to modern computing and networking technologies, students, staff, and faculty members at Project MAC, the Artificial Intelligence Laboratory, and the Tech Model Railroad Club wrote some of the earliest interactive computer video games like Spacewar! and created much of modern hacker slang and culture. Several major computer-related organizations have originated at MIT since the 1980s: Richard Stallman’s GNU Project and the subsequent Free Software Foundation were founded in the mid-1980s at the AI Lab; the MIT Media Lab was founded in 1985 by Nicholas Negroponte and Jerome Wiesner to promote research into novel uses of computer technology; the World Wide Web Consortium standards organization was founded at the Laboratory for Computer Science in 1994 by Tim Berners-Lee; the MIT OpenCourseWare project has made course materials for over 2,000 MIT classes available online free of charge since 2002; and the One Laptop per Child initiative to expand computer education and connectivity to children worldwide was launched in 2005.

    MIT was named a sea-grant college in 1976 to support its programs in oceanography and marine sciences and was named a space-grant college in 1989 to support its aeronautics and astronautics programs. Despite diminishing government financial support over the past quarter century, MIT launched several successful development campaigns to significantly expand the campus: new dormitories and athletics buildings on west campus; the Tang Center for Management Education; several buildings in the northeast corner of campus supporting research into biology, brain and cognitive sciences, genomics, biotechnology, and cancer research; and a number of new “backlot” buildings on Vassar Street including the Stata Center. Construction on campus in the 2000s included expansions of the Media Lab, the Sloan School’s eastern campus, and graduate residences in the northwest. In 2006, President Hockfield launched the MIT Energy Research Council to investigate the interdisciplinary challenges posed by increasing global energy consumption.

    In 2001, inspired by the open source and open access movements, MIT launched OpenCourseWare to make the lecture notes, problem sets, syllabi, exams, and lectures from the great majority of its courses available online for no charge, though without any formal accreditation for coursework completed. While the cost of supporting and hosting the project is high, OCW expanded in 2005 to include other universities as a part of the OpenCourseWare Consortium, which currently includes more than 250 academic institutions with content available in at least six languages. In 2011, MIT announced it would offer formal certification (but not credits or degrees) to online participants completing coursework in its “MITx” program, for a modest fee. The “edX” online platform supporting MITx was initially developed in partnership with Harvard and its analogous “Harvardx” initiative. The courseware platform is open source, and other universities have already joined and added their own course content. In March 2009 the MIT faculty adopted an open-access policy to make its scholarship publicly accessible online.

    MIT has its own police force. Three days after the Boston Marathon bombing of April 2013, MIT Police patrol officer Sean Collier was fatally shot by the suspects Dzhokhar and Tamerlan Tsarnaev, setting off a violent manhunt that shut down the campus and much of the Boston metropolitan area for a day. One week later, Collier’s memorial service was attended by more than 10,000 people, in a ceremony hosted by the MIT community with thousands of police officers from the New England region and Canada. On November 25, 2013, MIT announced the creation of the Collier Medal, to be awarded annually to “an individual or group that embodies the character and qualities that Officer Collier exhibited as a member of the MIT community and in all aspects of his life”. The announcement further stated that “Future recipients of the award will include those whose contributions exceed the boundaries of their profession, those who have contributed to building bridges across the community, and those who consistently and selflessly perform acts of kindness”.

    In September 2017, the school announced the creation of an artificial intelligence research lab called the MIT-IBM Watson AI Lab. IBM will spend $240 million over the next decade, and the lab will be staffed by MIT and IBM scientists. In October 2018 MIT announced that it would open a new Schwarzman College of Computing dedicated to the study of artificial intelligence, named after lead donor and The Blackstone Group CEO Stephen Schwarzman. The focus of the new college is to study not just AI, but interdisciplinary AI education, and how AI can be used in fields as diverse as history and biology. The cost of buildings and new faculty for the new college is expected to be $1 billion upon completion.

    The Caltech/MIT Advanced aLIGO (US) was designed and constructed by a team of scientists from California Institute of Technology, MIT, and industrial contractors, and funded by the National Science Foundation (US) .

    MIT/Caltech Advanced aLigo .

    It was designed to open the field of gravitational-wave astronomy through the detection of gravitational waves predicted by general relativity. Gravitational waves were detected for the first time by the LIGO detector in 2015. For contributions to the LIGO detector and the observation of gravitational waves, two Caltech physicists, Kip Thorne and Barry Barish, and MIT physicist Rainer Weiss won the Nobel Prize in physics in 2017. Weiss, who is also an MIT graduate, designed the laser interferometric technique, which served as the essential blueprint for the LIGO.

    The mission of MIT is to advance knowledge and educate students in science, technology, and other areas of scholarship that will best serve the nation and the world in the twenty-first century. We seek to develop in each member of the MIT community the ability and passion to work wisely, creatively, and effectively for the betterment of humankind.

     
  • richardmitnick 8:56 pm on May 18, 2021 Permalink | Reply
    Tags: "Diamonds engage both optical microscopy and MRI for better imaging", A relatively new type of biological tracer: microdiamonds that have had some of their carbon atoms kicked out and replaced by nitrogen., , , , Mechanical Enginering, , Microdiamonds are less than one-hundredth of an inch., Microdiamonds used as biological tracers, Microscopic diamond tracers can provide information via MRI and optical fluorescence simultaneously allowing scientists to get high-quality images 10 times deeper than light alone., Optics, When doctors or scientists want to peer into living tissue there’s always a trade-off between how deep they can probe and how clear a picture they can get.   

    From University of California-Berkeley (US): “Diamonds engage both optical microscopy and MRI for better imaging” 

    From University of California-Berkeley (US)

    May 17, 2021
    Robert Sanders
    rlsanders@berkeley.edu
    Media relations

    1
    The microdiamonds used as biological tracers are about 200 microns across, less than one-hundredth of an inch. They fluoresce red but can also be hyperpolarized, allowing them to be detected both optically — by fluorescence microscopy — and by radio-frequency NMR imaging, boosting the power of both techniques. Photo courtesy of Ashok Ajoy.

    When doctors or scientists want to peer into living tissue there’s always a trade-off between how deep they can probe and how clear a picture they can get.

    With light microscopes, researchers can see submicron-resolution structures inside cells or tissue, but only as deep as the millimeter or so that light can penetrate without scattering. Magnetic resonance imaging (MRI) uses radio frequencies that can reach everywhere in the body, but the technique provides low resolution — about a millimeter, or 1,000 times worse than light.

    A University of California, Berkeley, researcher has now shown that microscopic diamond tracers can provide information via MRI and optical fluorescence simultaneously potentially allowing scientists to get high-quality images up to a centimeter below the surface of tissue 10 times deeper than light alone.

    By using two modes of observation, the technique also could allow faster imaging.

    The technique would be useful primarily for studying cells and tissue outside the body, probing blood or other fluids for chemical markers of disease, or for physiological studies in animals.

    “This is perhaps the first demonstration that the same object can be imaged in optics and hyperpolarized MRI simultaneously,” said Ashok Ajoy, UC Berkeley assistant professor of chemistry. “There is a lot of information you can get in combination, because the two modes are better than the sum of their parts. This opens up many possibilities, where you can accelerate the imaging of these diamond tracers in a medium by several orders of magnitude.”

    The technique, which Ajoy and his colleagues report this week in the journal PNAS, utilizes a relatively new type of biological tracer: microdiamonds that have had some of their carbon atoms kicked out and replaced by nitrogen, leaving behind empty spots in the crystal — nitrogen vacancies — that fluoresce when hit by laser light.

    Ajoy exploits an isotope of carbon — carbon-13 (C-13) – that occurs naturally in the diamond particles at about 1% concentration, but also could be enriched further by replacing many of the dominant carbon atoms, carbon-12. Carbon-13 nuclei are more readily aligned, or polarized, by nearby spin-polarized vacancy centers, which become polarized at the same time they fluoresce after being illuminated with a laser. The polarized C-13 nuclei yield a stronger signal for nuclear magnetic resonance (NMR) — the technique at the heart of MRI.

    2
    The crystal lattice of a microdiamond contains gaps — nitrogen vacancies — that can be polarized (red spinning balls) and made to emit red light when illuminated by a laser. The polarized centers then hyperpolarize nearby carbon-13 atoms (blue balls), allowing them to be detected by NMR imaging. This allows the tracers to be imaged both by optical fluorescence microscopy and NMR, providing higher resolution pictures deeper inside tissue. UC Berkeley graphic by Xudong Lv and Mustafa Kamran.

    As a result, these hyperpolarized diamonds can be detected both optically — because of the fluorescent nitrogen vacancy centers — and at radio frequencies, because of the spin-polarized carbon-13. This allows simultaneous imaging by two of the best techniques available, with particular benefit when looking deep inside tissues that scatter visible light.

    “Optical imaging suffers greatly when you go in deep tissue. Even beyond 1 millimeter, you get a lot of optical scattering. This is a major problem,” Ajoy said. “The advantage here is that the imaging can be done in radio frequencies and optical light using the same diamond tracer. The same version of MRI that you use for imaging inside people can be used for imaging these diamond particles, even when the optical fluorescence signature is completely scattered out.”

    Detecting nuclear spin

    Ajoy focuses on improving NMR — a very precise way of identifying molecules — and its medical imaging counterpart, MRI, in hopes of lowering the cost and reducing the size of the machines. One limitation of NMR and MRI is that large, powerful and costly magnets are needed to align or polarize the nuclear spins of molecules inside samples or the body so that they can be detected by pulses of radio waves. But humans can’t withstand the very high magnetic fields needed to get lots of spins polarized at once, which would provide better images.

    3
    Emanuel Druga and Xudong Lv with a prototype “hyperpolarizer” for diamond particles (on table). They are standing next to a 9-tesla NMR machine. Credit: Ashok Ajoy.

    One way to overcome this is to tweak the nuclear spins of the atoms you want to detect so that more of them are aligned in the same direction, instead of randomly. With more spins aligned, called hyperpolarization, the signal detected by radio is stronger, and less powerful magnets can be used.

    In his latest experiments, Ajoy employed a magnetic field equivalent to that of a cheap refrigerator magnet and an inexpensive green laser to hyperpolarize the carbon-13 atoms in the crystal lattice of the microdiamonds.

    “It turns out that if you shine light on these particles, you can align their spins to a very, very high degree — about three to four orders of magnitude higher than the alignment of spins in an MRI machine,” Ajoy said. “Compared to conventional hospital MRIs, which use a magnetic field of 1.5 teslas, the carbons are polarized effectively like they were in a 1,000-tesla magnetic field.”

    When the diamonds are targeted to specific sites in cells or tissue — by antibodies, for example, which are often used with fluorescent tracers — they can be detected both by NMR imaging of the hyperpolarized C-13 and the fluorescence of the nitrogen vacancy centers in the diamond. The nitrogen vacancy-center diamonds are already becoming more widely used as tracers for their fluorescence alone.

    3
    In the researchers’ experiment, diamond particles arranged in a ring were imaged both optically and with magnetic resonance imaging (MRI). Credit: Ashok Ajoy.

    “We show one important cool feature of these diamond particles, the fact that they spin polarize — therefore they can glow very bright in an MRI machine — but they also fluoresce optically,” he said. “The same thing that endows them with the spin polarization also allows them to fluoresce optically.”

    The diamond tracers also are inexpensive and relatively easy to work with, Ajoy said. Together, these new developments could, in the future, allow for an inexpensive NMR imaging machine on every chemist’s benchtop. Today, only large hospitals can afford the million-dollar price tag for MRIs. He currently is working on other techniques to improve NMR and MRI, including using hyperpolarized diamond particles to hyperpolarize other molecules.

    The experiments were led by former graduate student Xudong Lv using a home-built hyperpolarizer device constructed by staff scientist Emanuel Druga. Ajoy’s work was supported by the Office of Naval Research (N00014-20-1-2806). Other co-authors are F. Wang, A. Aguilar, T. McKnelly, R. Nazaryan and L. Wu of UC Berkeley; J. H. Walton of University of California-Davis (US); O. Shenderova of Adamas Nanotechnologies Inc., in North Carolina; D. B. Vigneron of Univerity of California-San Fransisco (US); Carlos Meriles of City University of New York (US); and professor of chemical and biomolecular engineering Jeffrey Reimer and chemistry professor Alexander Pines, both of UC Berkeley.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The University of California-Berkeley is a public land-grant research university in Berkeley, California. Established in 1868 as the state’s first land-grant university, it was the first campus of the University of California (US) system and a founding member of the Association of American Universities (US). Its 14 colleges and schools offer over 350 degree programs and enroll some 31,000 undergraduate and 12,000 graduate students. Berkeley is ranked among the world’s top universities by major educational publications.

    Berkeley hosts many leading research institutes, including the Mathematical Sciences Research Institute and the Space Sciences Laboratory. It founded and maintains close relationships with three national laboratories at DOE’s Lawrence Berkeley National Laboratory(US), DOE’s Lawrence Livermore National Laboratory(US) and DOE’s Los Alamos National Lab(US), and has played a prominent role in many scientific advances, from the Manhattan Project and the discovery of 16 chemical elements to breakthroughs in computer science and genomics. Berkeley is also known for student activism and the Free Speech Movement of the 1960s.

    Berkeley alumni and faculty count among their ranks 110 Nobel laureates (34 alumni), 25 Turing Award winners (11 alumni), 14 Fields Medalists, 28 Wolf Prize winners, 103 MacArthur “Genius Grant” recipients, 30 Pulitzer Prize winners, and 19 Academy Award winners. The university has produced seven heads of state or government; five chief justices, including Chief Justice of the United States Earl Warren; 21 cabinet-level officials; 11 governors; and 25 living billionaires. It is also a leading producer of Fulbright Scholars, MacArthur Fellows, and Marshall Scholars. Berkeley alumni, widely recognized for their entrepreneurship, have founded many notable companies.

    Berkeley’s athletic teams compete in Division I of the NCAA, primarily in the Pac-12 Conference, and are collectively known as the California Golden Bears. The university’s teams have won 107 national championships, and its students and alumni have won 207 Olympic medals.

    Made possible by President Lincoln’s signing of the Morrill Act in 1862, the University of California was founded in 1868 as the state’s first land-grant university by inheriting certain assets and objectives of the private College of California and the public Agricultural, Mining, and Mechanical Arts College. Although this process is often incorrectly mistaken for a merger, the Organic Act created a “completely new institution” and did not actually merge the two precursor entities into the new university. The Organic Act states that the “University shall have for its design, to provide instruction and thorough and complete education in all departments of science, literature and art, industrial and professional pursuits, and general education, and also special courses of instruction in preparation for the professions”.

    Ten faculty members and 40 students made up the fledgling university when it opened in Oakland in 1869. Frederick H. Billings, a trustee of the College of California, suggested that a new campus site north of Oakland be named in honor of Anglo-Irish philosopher George Berkeley. The university began admitting women the following year. In 1870, Henry Durant, founder of the College of California, became its first president. With the completion of North and South Halls in 1873, the university relocated to its Berkeley location with 167 male and 22 female students.

    Beginning in 1891, Phoebe Apperson Hearst made several large gifts to Berkeley, funding a number of programs and new buildings and sponsoring, in 1898, an international competition in Antwerp, Belgium, where French architect Émile Bénard submitted the winning design for a campus master plan.

    20th century

    In 1905, the University Farm was established near Sacramento, ultimately becoming the University of California, Davis. In 1919, Los Angeles State Normal School became the southern branch of the University, which ultimately became the University of California, Los Angeles. By 1920s, the number of campus buildings had grown substantially and included twenty structures designed by architect John Galen Howard.

    In 1917, one of the nation’s first ROTC programs was established at Berkeley and its School of Military Aeronautics began training pilots, including Gen. Jimmy Doolittle. Berkeley ROTC alumni include former Secretary of Defense Robert McNamara and Army Chief of Staff Frederick C. Weyand as well as 16 other generals. In 1926, future fleet admiral Chester W. Nimitz established the first Naval ROTC unit at Berkeley.

    In the 1930s, Ernest Lawrence helped establish the Radiation Laboratory (now DOE’s Lawrence Berkeley National Laboratory (US)) and invented the cyclotron, which won him the Nobel physics prize in 1939. Using the cyclotron, Berkeley professors and Berkeley Lab researchers went on to discover 16 chemical elements—more than any other university in the world. In particular, during World War II and following Glenn Seaborg’s then-secret discovery of plutonium, Ernest Orlando Lawrence’s Radiation Laboratory began to contract with the U.S. Army to develop the atomic bomb. Physics professor J. Robert Oppenheimer was named scientific head of the Manhattan Project in 1942. Along with the Lawrence Berkeley National Laboratory, Berkeley founded and was then a partner in managing two other labs, Los Alamos National Laboratory (1943) and Lawrence Livermore National Laboratory (1952).

    By 1942, the American Council on Education ranked Berkeley second only to Harvard University (US) in the number of distinguished departments.

    In 1952, the University of California reorganized itself into a system of semi-autonomous campuses, with each campus given its own chancellor, and Clark Kerr became Berkeley’s first Chancellor, while Sproul remained in place as the President of the University of California.

    Berkeley gained a worldwide reputation for political activism in the 1960s. In 1964, the Free Speech Movement organized student resistance to the university’s restrictions on political activities on campus—most conspicuously, student activities related to the Civil Rights Movement. The arrest in Sproul Plaza of Jack Weinberg, a recent Berkeley alumnus and chair of Campus CORE, in October 1964, prompted a series of student-led acts of formal remonstrance and civil disobedience that ultimately gave rise to the Free Speech Movement, which movement would prevail and serve as precedent for student opposition to America’s involvement in the Vietnam War.

    In 1982, the Mathematical Sciences Research Institute (MSRI) was established on campus with support from the National Science Foundation and at the request of three Berkeley mathematicians — Shiing-Shen Chern, Calvin Moore and Isadore M. Singer. The institute is now widely regarded as a leading center for collaborative mathematical research, drawing thousands of visiting researchers from around the world each year.

    21st century

    In the current century, Berkeley has become less politically active and more focused on entrepreneurship and fundraising, especially for STEM disciplines.

    Modern Berkeley students are less politically radical, with a greater percentage of moderates and conservatives than in the 1960s and 70s. Democrats outnumber Republicans on the faculty by a ratio of 9:1. On the whole, Democrats outnumber Republicans on American university campuses by a ratio of 10:1.

    In 2007, the Energy Biosciences Institute was established with funding from BP and Stanley Hall, a research facility and headquarters for the California Institute for Quantitative Biosciences, opened. The next few years saw the dedication of the Center for Biomedical and Health Sciences, funded by a lead gift from billionaire Li Ka-shing; the opening of Sutardja Dai Hall, home of the Center for Information Technology Research in the Interest of Society; and the unveiling of Blum Hall, housing the Blum Center for Developing Economies. Supported by a grant from alumnus James Simons, the Simons Institute for the Theory of Computing was established in 2012. In 2014, Berkeley and its sister campus, Univerity of California-San Fransisco (US), established the Innovative Genomics Institute, and, in 2020, an anonymous donor pledged $252 million to help fund a new center for computing and data science.

    Since 2000, Berkeley alumni and faculty have received 40 Nobel Prizes, behind only Harvard and Massachusetts Institute of Technology (US) among US universities; five Turing Awards, behind only MIT and Stanford; and five Fields Medals, second only to Princeton University (US). According to PitchBook, Berkeley ranks second, just behind Stanford University, in producing VC-backed entrepreneurs.

    UC Berkeley Seal

     
  • richardmitnick 5:01 pm on May 10, 2021 Permalink | Reply
    Tags: "JQI Researchers Generate Tunable Twin Particles of Light", A new technique sees two distinct particles of light enter a chip and two identical twin particles of light leave it., , Identical twins might seem “indistinguishable” but in the quantum world the word takes on a new level of meaning., Inside a resonator a photon from each of the beams spontaneously combine. The researchers then observed how the photons reformed into two indistinguishable photons., , , Optics, Quantum interference— needed for quantum computers., , The resulting combination of being indistinguishable and entangled is essential for many potential uses of photons in quantum technologies.   

    From Joint Quantum Institute (US): “JQI Researchers Generate Tunable Twin Particles of Light” 

    JQI bloc

    At


    University of Maryland (US)

    May 10, 2021

    Story by Bailey Bedford

    Mohammad Hafezi
    hafezi@umd.edu

    1
    A new technique sees two distinct particles of light enter a chip and two identical twin particles of light leave it. The image artistically combines the journey of twin particles of light along the outer edge of a checkerboard of rings with the abstract shape of its topological underpinnings. Credit: Kaveh Haerian.

    Identical twins might seem “indistinguishable” but in the quantum world the word takes on a new level of meaning. While identical twins share many traits, the universe treats two indistinguishable quantum particles as intrinsically interchangeable. This opens the door for indistinguishable particles to interact in unique ways—such as in quantum interference—that are needed for quantum computers.

    While generating a crowd of photons—particles of light—is as easy as flipping a light switch, it’s trickier to make a pair of indistinguishable photons. And it takes yet more work to endow that pair with a quantum mechanical link known as entanglement. In a paper published May 10, 2021 in the journal Nature Photonics, JQI researchers and their colleagues describe a new way to make entangled twin particles of light and to tune their properties using a method conveniently housed on a chip, a potential boon for quantum technologies that require a reliable source of well-tailored photon pairs.

    The researchers, led by JQI fellow Mohammad Hafezi, designed the method to harness the advantages of topological physics. Topological physics explores previously untapped physical phenomena using the mathematical field of topology, which describes common traits shared by different shapes. (Where geometry concerns angles and sizes, topology is more about holes and punctures—all-encompassing characteristics that don’t depend on local details.) Researchers have made several major discoveries by applying this approach, which describes how quantum particles—like electrons or, in this case, photons—can move in a particular material or device by analyzing its broad characteristics through the lens of topological features that correspond to abstract shapes (such as the donut in the image above). The topological phenomena that have been revealed are directly tied to the general nature of the material; they must exist even in the presence of material impurities that would upset the smooth movement of photons or electrons in most other circumstances.

    Their new method builds on previous work, including the generation of a series of distinguishable photon pairs. In both the new and old experiments, the team created a checkerboard of rings on a silicon chip. Each ring is a resonator that acts like a tiny race track designed to keep certain photons traveling round and round for a long time. But since individual photons in a resonator live by quantum rules, the racecars (photons) can sometimes just pass unchanged through an intervening wall and proceed to speed along a neighboring track.

    The repeating grid of rings mimics the repeating grid of atoms that electrons travel through in a solid, allowing the researchers to design situations for light that mirror well known topological effects in electronics. By creating and exploring different topological environments, the team has developed new ways to manipulate photons.

    “It’s exactly the same mathematics that applies to electrons and photons,” says Sunil Mittal, a JQI postdoctoral researcher and the first author of the paper. “So you get more or less all the same topological features. All the mathematics that you do with electrons, you can simply carry to photonic systems.”

    In the current work, they recreated an electronic phenomenon called the anomalous quantum Hall effect that opens up paths for electrons on the edge of a material. These edge paths, which are called topological edge states, exist because of topological effects, and they can reliably transport electrons while leaving routes through the interior easily disrupted and impassable. Achieving this particular topological effect requires that localized magnetic fields push on electrons and that the total magnetic field when averaged over larger sections of the material cancels out to zero.

    But photons lack the electrical charge that makes electrons susceptible to magnetic shoves, so the team had to recreate the magnetic push in some other way. To achieve this, they laid out the tracks so that it is easier for the photons to quantum mechanically jump between rings in certain directions. This simulates the missing magnetic influence and creates an environment with a photonic version of the anomalous quantum Hall effect and its stable edge paths.

    For this experiment, the team sent two laser beams of two different colors (frequencies) of light into this carefully designed environment. Inside a resonator a photon from each of the beams spontaneously combine. The researchers then observed how the photons reformed into two indistinguishable photons, travelled through the topological edge paths and were eventually ejected from the chip.

    Since the new photons formed inside a resonator ring, they took on the traits (polarization and spatial mode) of the photons that the resonators are designed to hold. The only trait left that the team needed to worry about was their frequencies.

    The researchers matched the frequencies of the photons by selecting the appropriate input frequencies for the two lasers based on how they would combine inside the silicon resonators. With the appropriate theoretical understanding of the experiment, they can produce photons that are quantum mechanically indistinguishable.

    The nature of the formation of the new photons provides the desired quantum characteristics. The photons are quantum mechanically entangled due to the way they were generated as pairs; their combined properties—like the total energy of the pair—are constrained by what the original photons brought into the mix, so observing the property of one instantly reveals the equivalent fact about the other. Until they are observed—that is, detected by the researchers—they don’t exist as two individual particles with distinct quantum states for their frequencies. Rather, they are identical mixtures of possible frequency states called a superposition. The two photons being indistinguishable means they can quantum mechanically interfere with each other

    The resulting combination of being indistinguishable and entangled is essential for many potential uses of photons in quantum technologies. An additional lucky side effect of the researcher’s topological approach is that it gives them a greater ability to adjust the frequencies of the twin photons based on the frequencies they pump into the chip and how well the frequencies match with the topological states on the edge of the device.

    “This is not the only way to generate entangled photon pairs—there are many other devices—but they are not tunable,” Mittal says. “So once you fabricate your device, it is what it is. If you want to change the bandwidth of the photons or do something else, it’s not possible. But in our case, we don’t have to design a new device. We showed that, just by tuning the pump frequencies, we could tune the interference properties. So, that was very exciting.”

    The combination of the devices being tunable and robust against manufacturing imperfections make them an appealing option for practical applications, the authors say. The team plans to continue exploring the potential of this technique and related topological devices and possible ways to further improve the devices such as using other materials to make them.

    In addition to Hafezi and Mittal, former JQI graduate student Venkata Vikram Orre and former JQI postdoctoral researcher and current assistant professor at the University of Illinois Urbana-Champaign (US) Elizabeth Goldschmidt were also co-authors of the paper.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    JQI supported by Gordon and Betty Moore Foundation

    We are on the verge of a new technological revolution as the strange and unique properties of quantum physics become relevant and exploitable in the context of information science and technology.

    The Joint Quantum Institute (JQI) (US) is pursuing that goal through the work of leading quantum scientists from the Department of Physics of the University of Maryland (UMD (US)), the National Institute of Standards and Technology (NIST) and the Laboratory for Physical Sciences (LPS). Each institution brings to JQI major experimental and theoretical research programs that are dedicated to the goals of controlling and exploiting quantum systems.

    U Maryland Campus

    Driven by the pursuit of excellence, the University of Maryland (US) has enjoyed a remarkable rise in accomplishment and reputation over the past two decades. By any measure, Maryland is now one of the nation’s preeminent public research universities and on a path to become one of the world’s best. To fulfill this promise, we must capitalize on our momentum, fully exploit our competitive advantages, and pursue ambitious goals with great discipline and entrepreneurial spirit. This promise is within reach. This strategic plan is our working agenda.

    The plan is comprehensive, bold, and action oriented. It sets forth a vision of the University as an institution unmatched in its capacity to attract talent, address the most important issues of our time, and produce the leaders of tomorrow. The plan will guide the investment of our human and material resources as we strengthen our undergraduate and graduate programs and expand research, outreach and partnerships, become a truly international center, and enhance our surrounding community.

    Our success will benefit Maryland in the near and long term, strengthen the State’s competitive capacity in a challenging and changing environment and enrich the economic, social and cultural life of the region. We will be a catalyst for progress, the State’s most valuable asset, and an indispensable contributor to the nation’s well-being. Achieving the goals of Transforming Maryland requires broad-based and sustained support from our extended community. We ask our stakeholders to join with us to make the University an institution of world-class quality with world-wide reach and unparalleled impact as it serves the people and the state of Maryland.

     
  • richardmitnick 12:42 pm on May 4, 2021 Permalink | Reply
    Tags: "Nano flashlight enables new applications of light", , , , , Optics   

    From MIT : “Nano flashlight enables new applications of light” 

    MIT News

    From MIT

    May 4, 2021
    Elizabeth A. Thomson | Materials Research Laboratory

    1
    Schematic of three different nano flashlights for the generation of (left to right) focused, wide-spanning, and collimated light beams. Each flashlight could have different applications. Credit: Robin Singh.

    In work that could someday turn cell phones into sensors capable of detecting viruses and other minuscule objects, MIT researchers have built a powerful nanoscale flashlight on a chip.

    Their approach to designing the tiny light beam on a chip could also be used to create a variety of other nano flashlights with different beam characteristics for different applications. Think of a wide spotlight versus a beam of light focused on a single point.

    For many decades, scientists have used light to identify a material by observing how that light interacts with the material. They do so by essentially shining a beam of light on the material, then analyzing that light after it passes through the material. Because all materials interact with light differently, an analysis of the light that passes through the material provides a kind of “fingerprint” for that material. Imagine doing this for several colors — i.e., several wavelengths of light — and capturing the interaction of light with the material for each color. That would lead to a fingerprint that is even more detailed.

    Most instruments for doing this, known as spectrometers, are relatively large. Making them much smaller would have a number of advantages. For example, they could be portable and have additional applications (imagine a futuristic cell phone loaded with a self-contained sensor for a specific gas). However, while researchers have made great strides toward miniaturizing the sensor for detecting and analyzing the light that has passed through a given material, a miniaturized and appropriately shaped light beam—or flashlight—remains a challenge. Today that light beam is most often provided by macroscale equipment like a laser system that is not built into the chip itself as the sensors are.

    Complete sensor

    Enter the MIT work. In two recent papers in Nature Scientific Reports, researchers describe not only their approach for designing on-chip flashlights with a variety of beam characteristics, they also report building and successfully testing a prototype. Importantly, they created the device using existing fabrication technologies familiar to the microelectronics industry, so they are confident that the approach could be deployable at a mass scale with the lower cost that implies.

    Nature Scientific Reports

    Nature Scientific Reports

    Overall, this could enable industry to create a complete sensor on a chip with both light source and detector. As a result, the work represents a significant advance in the use of silicon photonics for the manipulation of light waves on microchips for sensor applications.

    “Silicon photonics has so much potential to improve and miniaturize the existing bench-scale biosensing schemes. We just need smarter design strategies to tap its full potential. This work shows one such approach,” says PhD candidate Robin Singh SM ’18, who is lead author of both papers.

    “This work is significant, and represents a new paradigm of photonic device design, enabling enhancements in the manipulation of optical beams,” says Dawn Tan, an associate professor at the Singapore University of Technology and Design (SUTD) (SG) who was not involved in the research.

    The senior coauthors on the first paper are Anuradha “Anu” Murthy Agarwal, a principal research scientist in MIT’s Materials Research Laboratory, Microphotonics Center, and Initiative for Knowledge and Innovation in Manufacturing; and Brian W. Anthony, a principal research scientist in MIT’s Department of Mechanical Engineering. Singh’s coauthors on the second paper are Agarwal; Anthony; Yuqi Nie, now at Princeton University (US); and Mingye Gao, a graduate student in MIT’s Department of Electrical Engineering and Computer Science.

    How they did it

    Singh and colleagues created their overall design using multiple computer modeling tools. These included conventional approaches based on the physics involved in the propagation and manipulation of light, and more cutting-edge machine-learning techniques in which the computer is taught to predict potential solutions using huge amounts of data. “If we show the computer many examples of nano flashlights, it can learn how to make better flashlights,” says Anthony. Ultimately, “we can then tell the computer the pattern of light that we want, and it will tell us what the design of the flashlight needs to be.”

    All of these modeling tools have advantages and disadvantages; together they resulted in a final, optimal design that can be adapted to create flashlights with different kinds of light beams.

    The researchers went on to use that design to create a specific flashlight with a collimated beam, or one in which the rays of light are perfectly parallel to each other. Collimated beams are key to some types of sensors. The overall flashlight that the researchers made involved some 500 rectangular nanoscale structures of different dimensions that the team’s modeling predicted would enable a collimated beam. Nanostructures of different dimensions would lead to different kinds of beams that in turn are key to other applications.

    The tiny flashlight with a collimated beam worked. Not only that, it provided a beam that was five times more powerful than is possible with conventional structures. That’s partly because “being able to control the light better means that less is scattered and lost,” says Agarwal.

    Singh describes the excitement he felt upon creating that first flashlight. “It was great to see through a microscope what I had designed on a computer. Then we tested it, and it worked!”

    This research was supported, in part, by the MIT Skoltech Initiative.

    Additional MIT facilities and departments that made this work possible are the Department of Materials Science and Engineering, the Materials Research Laboratory, the Institute for Medical Engineering and Science, and MIT.nano.

    Overall, this could enable industry to create a complete sensor on a chip with both light source and detector. As a result, the work represents a significant advance in the use of silicon photonics for the manipulation of light waves on microchips for sensor applications.

    “Silicon photonics has so much potential to improve and miniaturize the existing bench-scale biosensing schemes. We just need smarter design strategies to tap its full potential. This work shows one such approach,” says PhD candidate Robin Singh SM ’18, who is lead author of both papers.

    “This work is significant, and represents a new paradigm of photonic device design, enabling enhancements in the manipulation of optical beams,” says Dawn Tan, an associate professor at the Singapore University of Technology and Design who was not involved in the research.

    The senior coauthors on the first paper are Anuradha “Anu” Murthy Agarwal, a principal research scientist in MIT’s Materials Research Laboratory, Microphotonics Center, and Initiative for Knowledge and Innovation in Manufacturing; and Brian W. Anthony, a principal research scientist in MIT’s Department of Mechanical Engineering. Singh’s coauthors on the second paper are Agarwal; Anthony; Yuqi Nie, now at Princeton University; and Mingye Gao, a graduate student in MIT’s Department of Electrical Engineering and Computer Science.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    MIT Seal

    Massachusetts Institute of Technology (MIT)(US) is a private land-grant research university in Cambridge, Massachusetts. The institute has an urban campus that extends more than a mile (1.6 km) alongside the Charles River. The institute also encompasses a number of major off-campus facilities such as the MIT Lincoln Laboratory, the Bates Center, and the Haystack Observatory, as well as affiliated laboratories such as the Broad and Whitehead Institutes.

    MIT Haystack Observatory, Westford, Massachusetts, USA, Altitude 131 m (430 ft).

    Founded in 1861 in response to the increasing industrialization of the United States, MIT adopted a European polytechnic university model and stressed laboratory instruction in applied science and engineering. It has since played a key role in the development of many aspects of modern science, engineering, mathematics, and technology, and is widely known for its innovation and academic strength. It is frequently regarded as one of the most prestigious universities in the world.

    As of December 2020, 97 Nobel laureates, 26 Turing Award winners, and 8 Fields Medalists have been affiliated with MIT as alumni, faculty members, or researchers. In addition, 58 National Medal of Science recipients, 29 National Medals of Technology and Innovation recipients, 50 MacArthur Fellows, 80 Marshall Scholars, 3 Mitchell Scholars, 22 Schwarzman Scholars, 41 astronauts, and 16 Chief Scientists of the U.S. Air Force have been affiliated with MIT. The university also has a strong entrepreneurial culture and MIT alumni have founded or co-founded many notable companies. MIT is a member of the Association of American Universities (AAU).

    Foundation and vision

    In 1859, a proposal was submitted to the Massachusetts General Court to use newly filled lands in Back Bay, Boston for a “Conservatory of Art and Science”, but the proposal failed. A charter for the incorporation of the Massachusetts Institute of Technology, proposed by William Barton Rogers, was signed by John Albion Andrew, the governor of Massachusetts, on April 10, 1861.

    Rogers, a professor from the University of Virginia, wanted to establish an institution to address rapid scientific and technological advances. He did not wish to found a professional school, but a combination with elements of both professional and liberal education, proposing that:

    The true and only practicable object of a polytechnic school is, as I conceive, the teaching, not of the minute details and manipulations of the arts, which can be done only in the workshop, but the inculcation of those scientific principles which form the basis and explanation of them, and along with this, a full and methodical review of all their leading processes and operations in connection with physical laws.

    The Rogers Plan reflected the German research university model, emphasizing an independent faculty engaged in research, as well as instruction oriented around seminars and laboratories.

    Early developments

    Two days after MIT was chartered, the first battle of the Civil War broke out. After a long delay through the war years, MIT’s first classes were held in the Mercantile Building in Boston in 1865. The new institute was founded as part of the Morrill Land-Grant Colleges Act to fund institutions “to promote the liberal and practical education of the industrial classes” and was a land-grant school. In 1863 under the same act, the Commonwealth of Massachusetts founded the Massachusetts Agricultural College, which developed as the University of Massachusetts Amherst. In 1866, the proceeds from land sales went toward new buildings in the Back Bay.

    MIT was informally called “Boston Tech”. The institute adopted the European polytechnic university model and emphasized laboratory instruction from an early date. Despite chronic financial problems, the institute saw growth in the last two decades of the 19th century under President Francis Amasa Walker. Programs in electrical, chemical, marine, and sanitary engineering were introduced, new buildings were built, and the size of the student body increased to more than one thousand.

    The curriculum drifted to a vocational emphasis, with less focus on theoretical science. The fledgling school still suffered from chronic financial shortages which diverted the attention of the MIT leadership. During these “Boston Tech” years, MIT faculty and alumni rebuffed Harvard University president (and former MIT faculty) Charles W. Eliot’s repeated attempts to merge MIT with Harvard College’s Lawrence Scientific School. There would be at least six attempts to absorb MIT into Harvard. In its cramped Back Bay location, MIT could not afford to expand its overcrowded facilities, driving a desperate search for a new campus and funding. Eventually, the MIT Corporation approved a formal agreement to merge with Harvard, over the vehement objections of MIT faculty, students, and alumni. However, a 1917 decision by the Massachusetts Supreme Judicial Court effectively put an end to the merger scheme.

    In 1916, the MIT administration and the MIT charter crossed the Charles River on the ceremonial barge Bucentaur built for the occasion, to signify MIT’s move to a spacious new campus largely consisting of filled land on a one-mile-long (1.6 km) tract along the Cambridge side of the Charles River. The neoclassical “New Technology” campus was designed by William W. Bosworth and had been funded largely by anonymous donations from a mysterious “Mr. Smith”, starting in 1912. In January 1920, the donor was revealed to be the industrialist George Eastman of Rochester, New York, who had invented methods of film production and processing, and founded Eastman Kodak. Between 1912 and 1920, Eastman donated $20 million ($236.6 million in 2015 dollars) in cash and Kodak stock to MIT.
    Curricular reforms

    In the 1930s, President Karl Taylor Compton and Vice-President (effectively Provost) Vannevar Bush emphasized the importance of pure sciences like physics and chemistry and reduced the vocational practice required in shops and drafting studios. The Compton reforms “renewed confidence in the ability of the Institute to develop leadership in science as well as in engineering”. Unlike Ivy League schools, MIT catered more to middle-class families, and depended more on tuition than on endowments or grants for its funding. The school was elected to the Association of American Universities in 1934.

    Still, as late as 1949, the Lewis Committee lamented in its report on the state of education at MIT that “the Institute is widely conceived as basically a vocational school”, a “partly unjustified” perception the committee sought to change. The report comprehensively reviewed the undergraduate curriculum, recommended offering a broader education, and warned against letting engineering and government-sponsored research detract from the sciences and humanities. The School of Humanities, Arts, and Social Sciences and the MIT Sloan School of Management were formed in 1950 to compete with the powerful Schools of Science and Engineering. Previously marginalized faculties in the areas of economics, management, political science, and linguistics emerged into cohesive and assertive departments by attracting respected professors and launching competitive graduate programs. The School of Humanities, Arts, and Social Sciences continued to develop under the successive terms of the more humanistically oriented presidents Howard W. Johnson and Jerome Wiesner between 1966 and 1980.

    MIT’s involvement in military science surged during World War II. In 1941, Vannevar Bush was appointed head of the federal Office of Scientific Research and Development and directed funding to only a select group of universities, including MIT. Engineers and scientists from across the country gathered at MIT’s Radiation Laboratory, established in 1940 to assist the British military in developing microwave radar. The work done there significantly affected both the war and subsequent research in the area. Other defense projects included gyroscope-based and other complex control systems for gunsight, bombsight, and inertial navigation under Charles Stark Draper’s Instrumentation Laboratory; the development of a digital computer for flight simulations under Project Whirlwind; and high-speed and high-altitude photography under Harold Edgerton. By the end of the war, MIT became the nation’s largest wartime R&D contractor (attracting some criticism of Bush), employing nearly 4000 in the Radiation Laboratory alone and receiving in excess of $100 million ($1.2 billion in 2015 dollars) before 1946. Work on defense projects continued even after then. Post-war government-sponsored research at MIT included SAGE and guidance systems for ballistic missiles and Project Apollo.

    These activities affected MIT profoundly. A 1949 report noted the lack of “any great slackening in the pace of life at the Institute” to match the return to peacetime, remembering the “academic tranquility of the prewar years”, though acknowledging the significant contributions of military research to the increased emphasis on graduate education and rapid growth of personnel and facilities. The faculty doubled and the graduate student body quintupled during the terms of Karl Taylor Compton, president of MIT between 1930 and 1948; James Rhyne Killian, president from 1948 to 1957; and Julius Adams Stratton, chancellor from 1952 to 1957, whose institution-building strategies shaped the expanding university. By the 1950s, MIT no longer simply benefited the industries with which it had worked for three decades, and it had developed closer working relationships with new patrons, philanthropic foundations and the federal government.

    In late 1960s and early 1970s, student and faculty activists protested against the Vietnam War and MIT’s defense research. In this period MIT’s various departments were researching helicopters, smart bombs and counterinsurgency techniques for the war in Vietnam as well as guidance systems for nuclear missiles. The Union of Concerned Scientists was founded on March 4, 1969 during a meeting of faculty members and students seeking to shift the emphasis on military research toward environmental and social problems. MIT ultimately divested itself from the Instrumentation Laboratory and moved all classified research off-campus to the MIT Lincoln Laboratory facility in 1973 in response to the protests. The student body, faculty, and administration remained comparatively unpolarized during what was a tumultuous time for many other universities. Johnson was seen to be highly successful in leading his institution to “greater strength and unity” after these times of turmoil. However six MIT students were sentenced to prison terms at this time and some former student leaders, such as Michael Albert and George Katsiaficas, are still indignant about MIT’s role in military research and its suppression of these protests. (Richard Leacock’s film, November Actions, records some of these tumultuous events.)

    In the 1980s, there was more controversy at MIT over its involvement in SDI (space weaponry) and CBW (chemical and biological warfare) research. More recently, MIT’s research for the military has included work on robots, drones and ‘battle suits’.

    Recent history

    MIT has kept pace with and helped to advance the digital age. In addition to developing the predecessors to modern computing and networking technologies, students, staff, and faculty members at Project MAC, the Artificial Intelligence Laboratory, and the Tech Model Railroad Club wrote some of the earliest interactive computer video games like Spacewar! and created much of modern hacker slang and culture. Several major computer-related organizations have originated at MIT since the 1980s: Richard Stallman’s GNU Project and the subsequent Free Software Foundation were founded in the mid-1980s at the AI Lab; the MIT Media Lab was founded in 1985 by Nicholas Negroponte and Jerome Wiesner to promote research into novel uses of computer technology; the World Wide Web Consortium standards organization was founded at the Laboratory for Computer Science in 1994 by Tim Berners-Lee; the OpenCourseWare project has made course materials for over 2,000 MIT classes available online free of charge since 2002; and the One Laptop per Child initiative to expand computer education and connectivity to children worldwide was launched in 2005.

    MIT was named a sea-grant college in 1976 to support its programs in oceanography and marine sciences and was named a space-grant college in 1989 to support its aeronautics and astronautics programs. Despite diminishing government financial support over the past quarter century, MIT launched several successful development campaigns to significantly expand the campus: new dormitories and athletics buildings on west campus; the Tang Center for Management Education; several buildings in the northeast corner of campus supporting research into biology, brain and cognitive sciences, genomics, biotechnology, and cancer research; and a number of new “backlot” buildings on Vassar Street including the Stata Center. Construction on campus in the 2000s included expansions of the Media Lab, the Sloan School’s eastern campus, and graduate residences in the northwest. In 2006, President Hockfield launched the MIT Energy Research Council to investigate the interdisciplinary challenges posed by increasing global energy consumption.

    In 2001, inspired by the open source and open access movements, MIT launched OpenCourseWare to make the lecture notes, problem sets, syllabi, exams, and lectures from the great majority of its courses available online for no charge, though without any formal accreditation for coursework completed. While the cost of supporting and hosting the project is high, OCW expanded in 2005 to include other universities as a part of the OpenCourseWare Consortium, which currently includes more than 250 academic institutions with content available in at least six languages. In 2011, MIT announced it would offer formal certification (but not credits or degrees) to online participants completing coursework in its “MITx” program, for a modest fee. The “edX” online platform supporting MITx was initially developed in partnership with Harvard and its analogous “Harvardx” initiative. The courseware platform is open source, and other universities have already joined and added their own course content. In March 2009 the MIT faculty adopted an open-access policy to make its scholarship publicly accessible online.

    MIT has its own police force. Three days after the Boston Marathon bombing of April 2013, MIT Police patrol officer Sean Collier was fatally shot by the suspects Dzhokhar and Tamerlan Tsarnaev, setting off a violent manhunt that shut down the campus and much of the Boston metropolitan area for a day. One week later, Collier’s memorial service was attended by more than 10,000 people, in a ceremony hosted by the MIT community with thousands of police officers from the New England region and Canada. On November 25, 2013, MIT announced the creation of the Collier Medal, to be awarded annually to “an individual or group that embodies the character and qualities that Officer Collier exhibited as a member of the MIT community and in all aspects of his life”. The announcement further stated that “Future recipients of the award will include those whose contributions exceed the boundaries of their profession, those who have contributed to building bridges across the community, and those who consistently and selflessly perform acts of kindness”.

    In September 2017, the school announced the creation of an artificial intelligence research lab called the MIT-IBM Watson AI Lab. IBM will spend $240 million over the next decade, and the lab will be staffed by MIT and IBM scientists. In October 2018 MIT announced that it would open a new Schwarzman College of Computing dedicated to the study of artificial intelligence, named after lead donor and The Blackstone Group CEO Stephen Schwarzman. The focus of the new college is to study not just AI, but interdisciplinary AI education, and how AI can be used in fields as diverse as history and biology. The cost of buildings and new faculty for the new college is expected to be $1 billion upon completion.

    The Laser Interferometer Gravitational-Wave Observatory (LIGO) was designed and constructed by a team of scientists from California Institute of Technology, MIT, and industrial contractors, and funded by the National Science Foundation.

    MIT/Caltech Advanced aLigo .

    It was designed to open the field of gravitational-wave astronomy through the detection of gravitational waves predicted by general relativity. Gravitational waves were detected for the first time by the LIGO detector in 2015. For contributions to the LIGO detector and the observation of gravitational waves, two Caltech physicists, Kip Thorne and Barry Barish, and MIT physicist Rainer Weiss won the Nobel Prize in physics in 2017. Weiss, who is also an MIT graduate, designed the laser interferometric technique, which served as the essential blueprint for the LIGO.

    The mission of MIT is to advance knowledge and educate students in science, technology, and other areas of scholarship that will best serve the nation and the world in the twenty-first century. We seek to develop in each member of the MIT community the ability and passion to work wisely, creatively, and effectively for the betterment of humankind.

    USPS “Forever” postage stamps celebrating Innovation at MIT.

    MIT Campus

     
  • richardmitnick 10:56 am on May 4, 2021 Permalink | Reply
    Tags: "SMART investigates the science behind varying performance of different colored LEDs", , , Optics   

    From MIT : “SMART investigates the science behind varying performance of different colored LEDs” 

    MIT News

    From MIT

    April 28, 2021
    Singapore-MIT Alliance for Research and Technology

    1
    An array of multicolored LEDs periodically arranged to give off visible light. A combination of InGaN-based red, blue, and green LEDs is essential to cover lighting demands efficiently in the entire visible spectrum.
    Credits: Singapore-MIT Alliance for Research and Technology

    Researchers from the Low Energy Electronic Systems (LEES) interdisciplinary research group at Singapore-MIT Alliance for Research and Technology (SMART), MIT’s research enterprise in Singapore, together with MIT and National University of Singapore (NUS) (SG), have found a method to quantify the distribution of compositional fluctuations in the indium gallium nitride (InGaN) quantum wells at different indium concentrations.

    InGaN light emitting diodes (LEDs) have revolutionized the field of solid-state lighting due to their high efficiencies and durability, and low costs. The color of the LED emission can be changed by varying the indium concentration in the InGaN compound, giving InGaN LEDs the potential to cover the entire visible spectrum. InGaN LEDs with relatively low amounts of indium compared to gallium, such as the blue, green, and cyan LEDs, have enjoyed significant commercial success for communication, industry, and automotive applications. However, LEDs with higher indium concentrations, such as red and amber LEDs, suffer from a drop in efficiency with the increasing amount of indium.

    Currently, red and amber LEDs are made using aluminum indium gallium phosphide (AlInGaP) instead of InGaN due to InGaN’s poor performance in the red and amber spectrum caused by the efficiency drop. Understanding and overcoming the efficiency drop is the first step toward developing InGaN LEDs covering the whole visible spectrum, which would significantly reduce production costs.

    In a paper recently published in Physical Review Materials, the team employed a multifaceted method to understand the origin of compositional fluctuations and their potential effect on the efficiency of InGaN LEDs. The accurate determination of compositional fluctuations is critical to understanding their role in reducing efficiency in InGaN LEDs with higher indium compositions.

    “The [origin of the] efficiency drop experienced in higher indium concentration InGaN LEDs is still unknown to this date,” says co-author Professor Silvija Gradecak of the Department of Materials Science and Engineering at NUS, who is also a principal investigator at SMART LEES and a visiting professor at MIT. “It is important to understand this efficiency drop to create solutions that will be able to overcome it. In order to do so, we have designed a method that is able to detect and study the compositional fluctuations in the InGaN quantum wells to determine its role in the efficiency drop.”

    The researchers developed a multifaceted method to detect indium compositional fluctuations in the InGaN quantum wells using synergistic investigation that combines complementary computational methods, advanced atomic-scale characterization, and autonomous algorithms for image processing.

    Tara Mishra, lead author and SMART PhD fellow, says, “This method developed and used in our research is of general applicability and can be adapted to other materials science investigations where compositional fluctuations need to be investigated.”

    “The method that we developed can be widely applied and provide significant value and impact on other materials science studies, where atomistic compositional fluctuations play an important role in material performance,” says Pieremanuele Canepa, co-author of the paper, principal investigator at SMART LEES, assistant professor in the departments of Materials Science and Engineering and Chemical and Biomolecular Engineering at NUS, and a former MIT postdoc. “The understanding of the atomic distribution of InGaN at varying indium concentrations is key to developing next-generation full-color displays using the InGaN LED platform.”

    The research found that the indium atoms are randomly distributed in a relatively low-indium content InGaN. On the other hand, partial phase separation is observed in higher indium content InGaN, where random compositional fluctuations are concurrent with pockets of indium-rich regions.

    The findings advanced the understanding of the atomic microstructure of the InGaN and its potential effect on the performance of LEDs, paving the way for future research to determine the role of compositional fluctuations in the new generation of InGaN LEDs and design strategies to prevent the degradation of these devices.

    The research was carried out by SMART and supported by the National Research Foundation Singapore under its Campus for Research Excellence And Technological Enterprise (CREATE) program.

    SMART’s LEES interdisciplinary research group is creating new integrated circuit technologies that result in increased functionality, lower power consumption, and higher performance for electronic systems. These integrated circuits of the future will impact applications in wireless communications, power electronics, LED lighting, and displays. LEES has a vertically integrated research team possessing expertise in materials, devices, and circuits, comprising multiple individuals with professional experience within the semiconductor industry. This ensures that the research is targeted to meet the needs of the semiconductor industry both within Singapore and globally.

    SMART was established by MIT in partnership with the NRF in 2007. SMART is the first entity in CREATE developed by NRF. SMART serves as an intellectual and innovation hub for research interactions between MIT and Singapore, undertaking cutting-edge research projects in areas of interest to both Singapore and MIT. SMART currently comprises an Innovation Center and five interdisciplinary research groups: Antimicrobial Resistance, Critical Analytics for Manufacturing Personalized-Medicine, Disruptive and Sustainable Technologies for Agricultural Precision, Future Urban Mobility, and LEES.

    See the full article here .


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    Please help promote STEM in your local schools.

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    MIT Seal

    Massachusetts Institute of Technology (MIT)(US) is a private land-grant research university in Cambridge, Massachusetts. The institute has an urban campus that extends more than a mile (1.6 km) alongside the Charles River. The institute also encompasses a number of major off-campus facilities such as the MIT Lincoln Laboratory, the Bates Center, and the Haystack Observatory, as well as affiliated laboratories such as the Broad and Whitehead Institutes.

    MIT Haystack Observatory, Westford, Massachusetts, USA, Altitude 131 m (430 ft).

    Founded in 1861 in response to the increasing industrialization of the United States, MIT adopted a European polytechnic university model and stressed laboratory instruction in applied science and engineering. It has since played a key role in the development of many aspects of modern science, engineering, mathematics, and technology, and is widely known for its innovation and academic strength. It is frequently regarded as one of the most prestigious universities in the world.

    As of December 2020, 97 Nobel laureates, 26 Turing Award winners, and 8 Fields Medalists have been affiliated with MIT as alumni, faculty members, or researchers. In addition, 58 National Medal of Science recipients, 29 National Medals of Technology and Innovation recipients, 50 MacArthur Fellows, 80 Marshall Scholars, 3 Mitchell Scholars, 22 Schwarzman Scholars, 41 astronauts, and 16 Chief Scientists of the U.S. Air Force have been affiliated with MIT. The university also has a strong entrepreneurial culture and MIT alumni have founded or co-founded many notable companies. MIT is a member of the Association of American Universities (AAU).

    Foundation and vision

    In 1859, a proposal was submitted to the Massachusetts General Court to use newly filled lands in Back Bay, Boston for a “Conservatory of Art and Science”, but the proposal failed. A charter for the incorporation of the Massachusetts Institute of Technology, proposed by William Barton Rogers, was signed by John Albion Andrew, the governor of Massachusetts, on April 10, 1861.

    Rogers, a professor from the University of Virginia, wanted to establish an institution to address rapid scientific and technological advances. He did not wish to found a professional school, but a combination with elements of both professional and liberal education, proposing that:

    The true and only practicable object of a polytechnic school is, as I conceive, the teaching, not of the minute details and manipulations of the arts, which can be done only in the workshop, but the inculcation of those scientific principles which form the basis and explanation of them, and along with this, a full and methodical review of all their leading processes and operations in connection with physical laws.

    The Rogers Plan reflected the German research university model, emphasizing an independent faculty engaged in research, as well as instruction oriented around seminars and laboratories.

    Early developments

    Two days after MIT was chartered, the first battle of the Civil War broke out. After a long delay through the war years, MIT’s first classes were held in the Mercantile Building in Boston in 1865. The new institute was founded as part of the Morrill Land-Grant Colleges Act to fund institutions “to promote the liberal and practical education of the industrial classes” and was a land-grant school. In 1863 under the same act, the Commonwealth of Massachusetts founded the Massachusetts Agricultural College, which developed as the University of Massachusetts Amherst. In 1866, the proceeds from land sales went toward new buildings in the Back Bay.

    MIT was informally called “Boston Tech”. The institute adopted the European polytechnic university model and emphasized laboratory instruction from an early date. Despite chronic financial problems, the institute saw growth in the last two decades of the 19th century under President Francis Amasa Walker. Programs in electrical, chemical, marine, and sanitary engineering were introduced, new buildings were built, and the size of the student body increased to more than one thousand.

    The curriculum drifted to a vocational emphasis, with less focus on theoretical science. The fledgling school still suffered from chronic financial shortages which diverted the attention of the MIT leadership. During these “Boston Tech” years, MIT faculty and alumni rebuffed Harvard University president (and former MIT faculty) Charles W. Eliot’s repeated attempts to merge MIT with Harvard College’s Lawrence Scientific School. There would be at least six attempts to absorb MIT into Harvard. In its cramped Back Bay location, MIT could not afford to expand its overcrowded facilities, driving a desperate search for a new campus and funding. Eventually, the MIT Corporation approved a formal agreement to merge with Harvard, over the vehement objections of MIT faculty, students, and alumni. However, a 1917 decision by the Massachusetts Supreme Judicial Court effectively put an end to the merger scheme.

    In 1916, the MIT administration and the MIT charter crossed the Charles River on the ceremonial barge Bucentaur built for the occasion, to signify MIT’s move to a spacious new campus largely consisting of filled land on a one-mile-long (1.6 km) tract along the Cambridge side of the Charles River. The neoclassical “New Technology” campus was designed by William W. Bosworth and had been funded largely by anonymous donations from a mysterious “Mr. Smith”, starting in 1912. In January 1920, the donor was revealed to be the industrialist George Eastman of Rochester, New York, who had invented methods of film production and processing, and founded Eastman Kodak. Between 1912 and 1920, Eastman donated $20 million ($236.6 million in 2015 dollars) in cash and Kodak stock to MIT.
    Curricular reforms

    In the 1930s, President Karl Taylor Compton and Vice-President (effectively Provost) Vannevar Bush emphasized the importance of pure sciences like physics and chemistry and reduced the vocational practice required in shops and drafting studios. The Compton reforms “renewed confidence in the ability of the Institute to develop leadership in science as well as in engineering”. Unlike Ivy League schools, MIT catered more to middle-class families, and depended more on tuition than on endowments or grants for its funding. The school was elected to the Association of American Universities in 1934.

    Still, as late as 1949, the Lewis Committee lamented in its report on the state of education at MIT that “the Institute is widely conceived as basically a vocational school”, a “partly unjustified” perception the committee sought to change. The report comprehensively reviewed the undergraduate curriculum, recommended offering a broader education, and warned against letting engineering and government-sponsored research detract from the sciences and humanities. The School of Humanities, Arts, and Social Sciences and the MIT Sloan School of Management were formed in 1950 to compete with the powerful Schools of Science and Engineering. Previously marginalized faculties in the areas of economics, management, political science, and linguistics emerged into cohesive and assertive departments by attracting respected professors and launching competitive graduate programs. The School of Humanities, Arts, and Social Sciences continued to develop under the successive terms of the more humanistically oriented presidents Howard W. Johnson and Jerome Wiesner between 1966 and 1980.

    MIT’s involvement in military science surged during World War II. In 1941, Vannevar Bush was appointed head of the federal Office of Scientific Research and Development and directed funding to only a select group of universities, including MIT. Engineers and scientists from across the country gathered at MIT’s Radiation Laboratory, established in 1940 to assist the British military in developing microwave radar. The work done there significantly affected both the war and subsequent research in the area. Other defense projects included gyroscope-based and other complex control systems for gunsight, bombsight, and inertial navigation under Charles Stark Draper’s Instrumentation Laboratory; the development of a digital computer for flight simulations under Project Whirlwind; and high-speed and high-altitude photography under Harold Edgerton. By the end of the war, MIT became the nation’s largest wartime R&D contractor (attracting some criticism of Bush), employing nearly 4000 in the Radiation Laboratory alone and receiving in excess of $100 million ($1.2 billion in 2015 dollars) before 1946. Work on defense projects continued even after then. Post-war government-sponsored research at MIT included SAGE and guidance systems for ballistic missiles and Project Apollo.

    These activities affected MIT profoundly. A 1949 report noted the lack of “any great slackening in the pace of life at the Institute” to match the return to peacetime, remembering the “academic tranquility of the prewar years”, though acknowledging the significant contributions of military research to the increased emphasis on graduate education and rapid growth of personnel and facilities. The faculty doubled and the graduate student body quintupled during the terms of Karl Taylor Compton, president of MIT between 1930 and 1948; James Rhyne Killian, president from 1948 to 1957; and Julius Adams Stratton, chancellor from 1952 to 1957, whose institution-building strategies shaped the expanding university. By the 1950s, MIT no longer simply benefited the industries with which it had worked for three decades, and it had developed closer working relationships with new patrons, philanthropic foundations and the federal government.

    In late 1960s and early 1970s, student and faculty activists protested against the Vietnam War and MIT’s defense research. In this period MIT’s various departments were researching helicopters, smart bombs and counterinsurgency techniques for the war in Vietnam as well as guidance systems for nuclear missiles. The Union of Concerned Scientists was founded on March 4, 1969 during a meeting of faculty members and students seeking to shift the emphasis on military research toward environmental and social problems. MIT ultimately divested itself from the Instrumentation Laboratory and moved all classified research off-campus to the MIT Lincoln Laboratory facility in 1973 in response to the protests. The student body, faculty, and administration remained comparatively unpolarized during what was a tumultuous time for many other universities. Johnson was seen to be highly successful in leading his institution to “greater strength and unity” after these times of turmoil. However six MIT students were sentenced to prison terms at this time and some former student leaders, such as Michael Albert and George Katsiaficas, are still indignant about MIT’s role in military research and its suppression of these protests. (Richard Leacock’s film, November Actions, records some of these tumultuous events.)

    In the 1980s, there was more controversy at MIT over its involvement in SDI (space weaponry) and CBW (chemical and biological warfare) research. More recently, MIT’s research for the military has included work on robots, drones and ‘battle suits’.

    Recent history

    MIT has kept pace with and helped to advance the digital age. In addition to developing the predecessors to modern computing and networking technologies, students, staff, and faculty members at Project MAC, the Artificial Intelligence Laboratory, and the Tech Model Railroad Club wrote some of the earliest interactive computer video games like Spacewar! and created much of modern hacker slang and culture. Several major computer-related organizations have originated at MIT since the 1980s: Richard Stallman’s GNU Project and the subsequent Free Software Foundation were founded in the mid-1980s at the AI Lab; the MIT Media Lab was founded in 1985 by Nicholas Negroponte and Jerome Wiesner to promote research into novel uses of computer technology; the World Wide Web Consortium standards organization was founded at the Laboratory for Computer Science in 1994 by Tim Berners-Lee; the OpenCourseWare project has made course materials for over 2,000 MIT classes available online free of charge since 2002; and the One Laptop per Child initiative to expand computer education and connectivity to children worldwide was launched in 2005.

    MIT was named a sea-grant college in 1976 to support its programs in oceanography and marine sciences and was named a space-grant college in 1989 to support its aeronautics and astronautics programs. Despite diminishing government financial support over the past quarter century, MIT launched several successful development campaigns to significantly expand the campus: new dormitories and athletics buildings on west campus; the Tang Center for Management Education; several buildings in the northeast corner of campus supporting research into biology, brain and cognitive sciences, genomics, biotechnology, and cancer research; and a number of new “backlot” buildings on Vassar Street including the Stata Center. Construction on campus in the 2000s included expansions of the Media Lab, the Sloan School’s eastern campus, and graduate residences in the northwest. In 2006, President Hockfield launched the MIT Energy Research Council to investigate the interdisciplinary challenges posed by increasing global energy consumption.

    In 2001, inspired by the open source and open access movements, MIT launched OpenCourseWare to make the lecture notes, problem sets, syllabi, exams, and lectures from the great majority of its courses available online for no charge, though without any formal accreditation for coursework completed. While the cost of supporting and hosting the project is high, OCW expanded in 2005 to include other universities as a part of the OpenCourseWare Consortium, which currently includes more than 250 academic institutions with content available in at least six languages. In 2011, MIT announced it would offer formal certification (but not credits or degrees) to online participants completing coursework in its “MITx” program, for a modest fee. The “edX” online platform supporting MITx was initially developed in partnership with Harvard and its analogous “Harvardx” initiative. The courseware platform is open source, and other universities have already joined and added their own course content. In March 2009 the MIT faculty adopted an open-access policy to make its scholarship publicly accessible online.

    MIT has its own police force. Three days after the Boston Marathon bombing of April 2013, MIT Police patrol officer Sean Collier was fatally shot by the suspects Dzhokhar and Tamerlan Tsarnaev, setting off a violent manhunt that shut down the campus and much of the Boston metropolitan area for a day. One week later, Collier’s memorial service was attended by more than 10,000 people, in a ceremony hosted by the MIT community with thousands of police officers from the New England region and Canada. On November 25, 2013, MIT announced the creation of the Collier Medal, to be awarded annually to “an individual or group that embodies the character and qualities that Officer Collier exhibited as a member of the MIT community and in all aspects of his life”. The announcement further stated that “Future recipients of the award will include those whose contributions exceed the boundaries of their profession, those who have contributed to building bridges across the community, and those who consistently and selflessly perform acts of kindness”.

    In September 2017, the school announced the creation of an artificial intelligence research lab called the MIT-IBM Watson AI Lab. IBM will spend $240 million over the next decade, and the lab will be staffed by MIT and IBM scientists. In October 2018 MIT announced that it would open a new Schwarzman College of Computing dedicated to the study of artificial intelligence, named after lead donor and The Blackstone Group CEO Stephen Schwarzman. The focus of the new college is to study not just AI, but interdisciplinary AI education, and how AI can be used in fields as diverse as history and biology. The cost of buildings and new faculty for the new college is expected to be $1 billion upon completion.

    The Laser Interferometer Gravitational-Wave Observatory (LIGO) was designed and constructed by a team of scientists from California Institute of Technology, MIT, and industrial contractors, and funded by the National Science Foundation.

    MIT/Caltech Advanced aLigo .

    It was designed to open the field of gravitational-wave astronomy through the detection of gravitational waves predicted by general relativity. Gravitational waves were detected for the first time by the LIGO detector in 2015. For contributions to the LIGO detector and the observation of gravitational waves, two Caltech physicists, Kip Thorne and Barry Barish, and MIT physicist Rainer Weiss won the Nobel Prize in physics in 2017. Weiss, who is also an MIT graduate, designed the laser interferometric technique, which served as the essential blueprint for the LIGO.

    The mission of MIT is to advance knowledge and educate students in science, technology, and other areas of scholarship that will best serve the nation and the world in the twenty-first century. We seek to develop in each member of the MIT community the ability and passion to work wisely, creatively, and effectively for the betterment of humankind.

    USPS “Forever” postage stamps celebrating Innovation at MIT.

    MIT Campus

     
  • richardmitnick 4:55 pm on May 3, 2021 Permalink | Reply
    Tags: "Shaped light waves penetrate further into photonic crystals", , , Optics, ,   

    From physicsworld.com (UK) : “Shaped light waves penetrate further into photonic crystals” 

    From physicsworld.com (UK)

    03 May 2021
    Isabelle Dumé

    1
    Light propagation inside a photonic crystal with shaped and unshaped incident light waves. Courtesy: R Uppu.

    An international team of researchers has succeeded in steering light waves deep into “forbidden” regions of photonic crystals by manipulating the shape of the waves. The technique, which was developed by scientists at the University of Twente [ Universiteit Twente] (NL), the University of Iowa (US) and the University of Copenhagen [Københavns Universitet](DK), takes advantage of nanoscale channels created naturally when the crystals are fabricated, and could find use in a host of optoelectronics applications.

    Photonic crystals are made by etching patterned nanopores into a substrate such as a silicon wafer. These patterned structures are specially designed to make the crystal’s refractive index vary periodically on the length scale of visible light. This periodic variation, in turn, produces a photonic “band gap” that affects how photons propagate through the crystal – similar to the way a periodic potential in semiconductors affects the flow of electrons by defining allowed and forbidden energy bands.

    The presence of this band gap means that only light within certain wavelength ranges can pass through the crystal. Outside these ranges, the light is reflected due to an effect called Bragg interference. The prohibition on light travel at forbidden wavelengths is so restrictive that if a quantum dot that emits light at one of these wavelengths is placed inside the crystal, it stops emitting the forbidden colour of light.

    “Out of control”

    Photonic crystals were discovered 30 years ago, and they are now routinely integrated into devices such as light sources, lasers, efficient solar cells and so-called invisibility cloaks. They are also used to trap light in extremely small volumes and to process optical information. In addition, the ability to tightly control their emission properties makes them attractive for advanced applications such as nonlinear processors for quantum computing and memories that store information encoded as light.

    To date, all these applications have been static, because the structure of the crystals (and thus the path of the light transported within them) is fixed. New functionalities should be possible, however, if light can be controllably steered anywhere inside the crystals, beyond the depth set by Bragg interference.

    “This depth is known as the Bragg length and is determined by the intentionally introduced periodic structural order in the crystal when it is fabricated,” explains study lead author Ravitej Uppu. “Disorder arising from unavoidable imperfections in the nanofabrication process, however, produces channels that penetrate deep into the crystal and through which the trajectory of incoming light waves can be deviated. These channels are usually detrimental for applications because they allow a small fraction of waves to ‘get out of control’ and randomly scatter into the crystal.”

    Light-steering demonstration

    Led by Willem Vos of the University of Twente, Uppu and colleagues have now turned these channels and the fact that light waves can travel through them into an advantage. They did this by shaping the wavefronts of light waves so that they selectively couple to these channels, thus allowing the waves to travel much further into the crystal. What is more, by programming the wavefronts correctly, they could interfere the waves such that their intensity concentrates at a single location deep inside the crystals.

    In their work, published in Physical Review Letters, the researchers studied light propagation in two-dimensional photonic crystals consisting of large periodic arrays of pores (about 6 microns deep) etched in a silicon wafer. They began by directing unstructured, random, plane light waves onto the crystals and imaging the light that leaks through the structures’ top surface. This leaked light revealed the energy density of light at any given position inside the crystals, and as the researchers expected, they saw hardly any sign that light had penetrated the crystal at all. They confirmed this result by showing that 95% of the incident light was reflected.

    Eight times the Bragg length

    The researchers then repeated their experiment using light waves with wavefronts shaped using a device known as a spatial light modulator. By programming the shapes, they managed to steer the waves into otherwise forbidden gaps in the crystal, travelling up to eight times the Bragg length. Focusing this light allowed them to create a bright spot that is up to 100 times more intense compared to that created by unshaped wavefronts.

    Members of the team say they now plan to extend their experiments to 3D photonic band gap crystals, where they “eagerly expect” to see additional phenomena such as Anderson localization of light. “Such 3D control of light transport could be exploited for exotic light hopping across a lattice of cavities inside these crystals,” Uppu tells Physics World. “The combination of reconfigurable light transport and cavities could potentially allow us to realize nonlinear quantum operations for quantum computing.”

    And that is not all. Since the observed phenomena are essentially exploiting wave interference, the team is confident that their results can be generalized to electron waves, magnetic spin waves or even sound waves. Indeed, Uppu notes that other researchers have recently made considerable advances in the latter two fields, so the required spatial shaping of these waves should be feasible.

    See the full article here .


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    Please help promote STEM in your local schools.

    a href=”http://www.stemedcoalition.org/”>Stem Education Coalition

    PhysicsWorld(UK) is a publication of the Institute of Physics(UK). The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application.

    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.
    IOP Institute of Physics

     
  • richardmitnick 5:34 pm on April 20, 2021 Permalink | Reply
    Tags: "Combining Light and Superconductors Could Boost AI Capabilities", , , By operating at low temperature superconducting electronic circuits; single-photon detectors; silicon light sources we will open a path toward rich functionality and scalable fabrication., Optics, , , The fabrication of silicon chips with electronic and photonic circuit elements is difficult for many physical and practical reasons related to the materials used for the components.   

    From American Institute of Physics-AIP (US) : “Combining Light and Superconductors Could Boost AI Capabilities” 

    From American Institute of Physics-AIP (US)

    April 20, 2021
    Larry Frum
    media@aip.org
    301-209-3090

    1
    Spatial hierarchy. CREDIT: Jeffrey Michael Shainline.

    As artificial intelligence has attracted broad interest, researchers are focused on understanding how the brain accomplishes cognition so they can construct artificial systems with general intelligence comparable to humans’ intelligence.

    Many have approached this challenge by using conventional silicon microelectronics in conjunction with light. However, the fabrication of silicon chips with electronic and photonic circuit elements is difficult for many physical and practical reasons related to the materials used for the components.

    In Applied Physics Letters, by AIP Publishing, researchers at the National Institute of Standards and Technology (US) propose an approach to large-scale artificial intelligence that focuses on integrating photonic components with superconducting electronics rather than semiconducting electronics.

    “We argue that by operating at low temperature and using superconducting electronic circuits; single-photon detectors; and silicon light sources we will open a path toward rich computational functionality and scalable fabrication,” said author Jeffrey Shainline.

    Using light for communication in conjunction with complex electronic circuits for computation could enable artificial cognitive systems of scale and functionality beyond what can be achieved with either light or electronics alone.

    “What surprised me most was that optoelectronic integration may be much easier when working at low temperatures and using superconductors than when working at room temperatures and using semiconductors,” said Shainline.

    Superconducting photon detectors enable detection of a single photon, while semiconducting photon detectors require about 1,000 photons. So not only do silicon light sources work at 4 kelvins, but they also can be 1,000 times less bright than their room temperature counterparts and still communicate effectively.

    Some applications, such as chips in cellphones, require working at room temperature, but the proposed technology would still have wide reaching applicability for advanced computing systems.

    The researchers plan to explore more complex integration with other superconducting electronic circuits as well as demonstrate all the components that comprise artificial cognitive systems, including synapses and neurons.

    Showing that the hardware can be manufactured in a scalable manner, so large systems can be realized at a reasonable cost, will also be important. Superconducting optoelectronic integration could also help create scalable quantum technologies based on superconducting or photonic qubits. Such quantum-neural hybrid systems may also lead to new ways of leveraging the strengths of quantum entanglement with spiking neurons.

    See the full article here.

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The American Institute of Physics (AIP) promotes science and the profession of physics, publishes physics journals, and produces publications for scientific and engineering societies. The AIP is made up of various member societies. Its corporate headquarters are at the American Center for Physics in College Park, Maryland, but the institute also has offices in Melville, New York, and Beijing.

    The focus of the AIP appears to be organized around a set of core activities. The first delineated activity is to support member societies regarding essential society functions. This is accomplished by annually convening the various society officers to discuss common areas of concern. A range of topics is discussed which includes scientific publishing, public policy issues, membership-base issues, philanthropic giving, science education, science careers for a diverse population, and a forum for sharing ideas.

    Another core activity is publishing the science of physics in research journals, magazines, and conference proceedings. Member societies continue nevertheless to publish their own journals.

    Other core activities are tracking employment and education trends with six decades of coverage, being a liaison between research science and industry, historical collections and physics outreach programs, and supporting science education initiatives and supporting undergraduate physics. One other core activity is as an advocate for science policy to the U.S. Congress and the general public.

    Member societies:
    Acoustical Society of America
    American Association of Physicists in Medicine
    American Association of Physics Teachers
    American Astronomical Society
    American Crystallographic Association
    American Meteorological Society
    American Physical Society
    American Vacuum Society

    Affiliated societies

    American Association for the Advancement of Science, Section on Physics
    American Chemical Society, Division of Physical Chemistry
    American Institute of Aeronautics and Astronautics
    American Nuclear Society
    American Society of Civil Engineers
    ASM International
    Astronomical Society of the Pacific
    Biomedical Engineering Society
    Council on Undergraduate Research, Physics & Astronomy Division
    Electrochemical Society
    Geological Society of America
    IEEE Nuclear and Plasma Sciences Society
    International Association of Mathematical Physics
    International Union of Crystallography
    International Centre for Diffraction Data
    Health Physics Society

     
  • richardmitnick 4:28 pm on March 8, 2021 Permalink | Reply
    Tags: Accelerometers keep rockets and airplanes on the correct flight path; provide navigation for self-driving cars; and rotate images so that they stay right-side up on cellphones and tablets among other , , , Optics, Optomechanical accelerometer, , Researchers at the National Institute of Standards and Technology (NIST) have developed an accelerometer a mere millimeter thick that uses laser light instead of mechanical strain to produce a signal.   

    From National Institute of Standards and Technology(US): “A Better Way to Measure Acceleration” 


    From National Institute of Standards and Technology(US)

    March 08, 2021

    NIST researchers rely on a light touch.

    Media Contact
    Ben P. Stein
    benjamin.stein@nist.gov
    (301) 975-2763

    Technical Contact
    Jason J. Gorman
    jason.gorman@nist.gov
    (301) 975-3446

    1
    Illustration of an optomechanical accelerometer, which uses light to measure acceleration. The NIST device consists of two silicon chips, with infrared laser light entering at the bottom chip and exiting at the top. The top chip contains a proof mass suspended by silicon beams, which enables the mass to move up and down freely in response to acceleration. A mirrored coating on the proof mass and a hemispherical mirror attached to the bottom chip form an optical cavity. The wavelength of the infrared light is chosen so that it nearly matches the resonant wavelength of the cavity, enabling the light to build in intensity as it bounces back and forth between the two mirrored surfaces many times before exiting. When the device experiences an acceleration, the proof mass moves, changing the length of the cavity and shifting the resonant wavelength. This alters the intensity of the reflected light. An optical readout converts the change in intensity into a measurement of acceleration.

    You’re going at the speed limit down a two-lane road when a car barrels out of a driveway on your right. You slam on the brakes, and within a fraction of a second of the impact an airbag inflates, saving you from serious injury or even death.

    The airbag deploys thanks to an accelerometer — a sensor that detects sudden changes in velocity. Accelerometers keep rockets and airplanes on the correct flight path; provide navigation for self-driving cars; and rotate images so that they stay right-side up on cellphones and tablets among other essential tasks.

    Addressing the increasing demand to accurately measure acceleration in smaller navigation systems and other devices, researchers at the National Institute of Standards and Technology (NIST) have developed an accelerometer a mere millimeter thick that uses laser light instead of mechanical strain to produce a signal.

    Although a few other accelerometers also rely on light, the design of the NIST instrument makes the measuring process more straightforward, providing higher accuracy. It also operates over a greater range of frequencies and has been more rigorously tested than similar devices.

    Not only is the NIST device, known as an optomechanical accelerometer, much more precise than the best commercial accelerometers, it does not need to undergo the time-consuming process of periodic calibrations. In fact, because the instrument uses laser light of a known frequency to measure acceleration, it may ultimately serve as a portable reference standard to calibrate other accelerometers now on the market, making them more accurate.

    The accelerometer also has the potential to improve inertial navigation in such critical systems as military aircraft, satellites and submarines, especially when a GPS signal is not available. NIST researchers Jason Gorman, Thomas LeBrun, David Long and their colleagues describe their work in the journal Optica.

    The study is part of “NIST on a Chip”, a program that brings the institute’s cutting-edge measurement-science technology and expertise directly to users in commerce, medicine, defense and academia.

    Accelerometers, including the new NIST device, record changes in velocity by tracking the position of a freely moving mass, dubbed the “proof mass,” relative to a fixed reference point inside the device. The distance between the proof mass and the reference point only changes if the accelerometer slows down, speeds up or switches direction. The same is true if you’re a passenger in a car. If the car is either at rest or moving at constant velocity, the distance between you and the dashboard stays the same. But if the car suddenly brakes, you’re thrown forward and the distance between you and the dashboard decreases.

    The motion of the proof mass creates a detectable signal. The accelerometer developed by NIST researchers relies on infrared light to measure the change in distance between two highly reflective surfaces that bookend a small region of empty space. The proof mass, which is suspended by flexible beams one-fifth the width of a human hair so that it can move freely, supports one of the mirrored surfaces. The other reflecting surface, which serves as the accelerometer’s fixed reference point, consists of an immovable microfabricated concave mirror.

    Together, the two reflecting surfaces and the empty space between them form a cavity in which infrared light of just the right wavelength can resonate, or bounce back and forth, between the mirrors, building in intensity. That wavelength is determined by the distance between the two mirrors, much as the pitch of a plucked guitar depends on the distance between the instrument’s fret and bridge. If the proof mass moves in response to acceleration, changing the separation between the mirrors, the resonant wavelength also changes.

    To track the changes in the cavity’s resonant wavelength with high sensitivity, a stable single-frequency laser is locked to the cavity. As described in a recent publication in Optics Letters, the researchers have also employed an optical frequency comb — a device that can be used as a ruler to measure the wavelength of light — to measure the cavity length with high accuracy. The markings of the ruler (the teeth of the comb) can be thought of as a series of lasers with equally spaced wavelengths. When the proof mass moves during a period of acceleration, either shortening or lengthening the cavity, the intensity of the reflected light changes as the wavelengths associated with the comb’s teeth move in and out of resonance with the cavity.

    Accurately converting the displacement of the proof mass into an acceleration is a critical step that has been problematic in most existing optomechanical accelerometers. However, the team’s new design ensures that the dynamic relationship between the displacement of the proof mass and the acceleration is simple and easy to model through first principles of physics. In short, the proof mass and supporting beams are designed so that they behave like a simple spring, or harmonic oscillator, that vibrates at a single frequency in the operating range of the accelerometer.

    This simple dynamic response enabled the scientists to achieve low measurement uncertainty over a wide range of acceleration frequencies — 1 kilohertz to 20 kilohertz — without ever having to calibrate the device. This feature is unique because all commercial accelerometers have to be calibrated, which is time-consuming and expensive. Since the publication of their study in Optica, the researchers have made several improvements that should decrease their device’s uncertainty to nearly 1%.

    Capable of sensing displacements of the proof mass that are less than one hundred-thousandth the diameter of a hydrogen atom, the optomechanical accelerometer detects accelerations as tiny as 32 billionths of a g, where g is the acceleration due to Earth’s gravity. That’s a higher sensitivity than all accelerometers now on the market with similar size and bandwidth.

    With further improvements, the NIST optomechanical accelerometer could be used as a portable, high-accuracy reference device to calibrate other accelerometers without having to bring them into a laboratory.

    See the full article here.

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    NIST Campus, Gaitherberg, MD, USA

    National Institute of Standards and Technology(US)‘s Mission, Vision, Core Competencies, and Core Values

    Mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.

    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.

    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

     
  • richardmitnick 11:25 pm on March 5, 2021 Permalink | Reply
    Tags: "Light in concert with force reveals how materials become harder when illuminated", "Photoindentation": a technique for quantitatively studying the effect of light on nanoscale mechanical properties of thin wafers of semiconductors or any other crystalline material., "Photoindentation": a tiny pointy probe indents the material while it is illuminated by light under controlled conditions., , Nagoya University [名古屋大学; Nagoya daigaku](JP), , Optics, , , Semiconductor materials play an indispensable role in our modern information-oriented society., Technical University of Darmstadt [Technische Universität Darmstadt](DE), The new findings demonstrate that purely plastic deformation without crack formation in semiconductor materials occurs at the nanoscale., There is an urgent need for the strength of semiconductor materials to be reappraised under controlled illumination conditions and thin sample sizes., This newly established robust experimental protocol makes it possible to evaluate the effect of light on the strength of even non-semiconducting materials that are very thin., Using a transmission electron microscope the researchers observe the effect of light at a range of wavelengths on dislocation nucleation.   

    From Nagoya University [名古屋大学; Nagoya daigaku](JP) and Technical University of Darmstadt [Technische Universität Darmstadt](DE) via phys.org: “Light in concert with force reveals how materials become harder when illuminated” 

    From Nagoya University [名古屋大学; Nagoya daigaku](JP)

    and

    [Technische Universität Darmstadt](DE)

    via


    From phys.org

    March 5, 2021

    1
    Schematic illustration of how light affects the nucleation (birth) of dislocations (slippages of crystal planes) and dislocation motion, when the sample is also placed under mechanical loading. The Nagoya University/Technical University of Darmstadt research collaboration has found clear evidence that propagation of dislocations in semiconductors is suppressed by light. The likely cause is interaction between dislocations and electrons and holes excited by the light. Credit: Atsutomo Nakamura.

    Semiconductor materials play an indispensable role in our modern information-oriented society. For reliable performance of semiconductor devices, these materials need to have superior mechanical properties: they must be strong as well as resistant to fracture, despite being rich in nanoscale structures.

    Recently, it has become increasingly clear that the optical environment affects the structural strength of semiconductor materials. The effect can be much more significant than expected, especially in light-sensitive semiconductors, and particularly since due to technological constraints or fabrication cost many semiconductors can only be mass-produced in very small and thin sizes. Moreover, laboratory testing of their strength has generally been performed on large samples. In the light of the recent explosion in emerging nanoscale applications, all of this suggests that there is an urgent need for the strength of semiconductor materials to be reappraised under controlled illumination conditions and thin sample sizes.

    To this end, Professor Atsutomo Nakamura’s group at Nagoya University [名古屋大学; Nagoya daigaku](JP) , and Dr. Xufei Fang’s group at the Technical University of Darmstadt [Technische Universität Darmstadt](DE)have developed a technique for quantitatively studying the effect of light on nanoscale mechanical properties of thin wafers of semiconductors or any other crystalline material. They call it a “photoindentation” method. Essentially, a tiny, pointy probe indents the material while it is illuminated by light under controlled conditions, and the depth and rate at which the probe indents the surface can be measured. The probe creates dislocations—slippages of crystal planes—near the surface, and using a transmission electron microscope the researchers observe the effect of light at a range of wavelengths on dislocation nucleation (the birth of new dislocations) and dislocation mobility (the dislocations’ gliding or sliding away from the point where they were created). The nucleation and mobility are measured separately for the first time and is one of the novelties of the photoindentation technique.

    The researchers have discovered that while light has a marginal effect on the generation of dislocations under mechanical loading, it has a much stronger effect on the motion of dislocations. When a dislocation occurs, it is energetically favorable for it to expand and join up (nucleate) with others, and the imperfection gets bigger. Illumination by light does not affect this: the electrons and holes excited in the semiconductor by the light (the photo-excited carriers) do not affect the strain energy of the dislocation, and it is this energy that determines the “line tension” of the dislocation that controls the nucleation process.

    On the other hand, dislocations can also move in a so-called ‘glide motion’, during which photo-excited carriers are dragged by dislocations via electrostatic interaction. The effect of photo-excited carriers on this dislocation motion is much more pronounced: if enough carriers are produced, the material becomes much stronger.

    This effect is strikingly demonstrated when the same experiment is carried out in complete darkness and then under illumination with light at a wavelength that matches the semiconductor band gap (which produces an increased number of photo-excited carriers). When indented, any solid material initially undergoes “plastic deformation”—changing shape without springing back, somewhat like putty—until the load becomes too great, upon which it cracks. The Nagoya University research group demonstrated that the inorganic semiconductor zinc sulfide (ZnS) in total darkness behaves somewhat like putty, deforming by a huge 45% under shear strain without cracking or falling apart. However, when illuminated at the correct wavelength, it becomes quite hard. At other wavelengths it becomes not quite as hard.

    The new findings [Nano Letters] demonstrate that purely plastic deformation without crack formation in semiconductor materials occurs at the nanoscale. With regards to mechanical behavior, these semiconductors therefore resemble metallic materials. This newly established robust experimental protocol makes it possible to evaluate the effect of light on the strength of even non-semiconducting materials that are very thin. Professor Nakamura notes: “One particularly important aspect is that non-semiconductors can exhibit semiconducting properties near the surface, due to oxidation, for instance, and since the starting point of deformation or fracture is often the surface, it is of great significance to establish a method for accurately measuring the strength of materials under controlled illumination conditions at the very surface, on a nanoscale.”

    The hardening effect that electron-hole pairs freed by light illumination have on material strength—by suppressing the propagation of dislocations particularly near the surface—is part of a paradigm shift in the science of material strength. Conventionally, when considering the strength of a material, the atomic arrangement was the smallest unit. In other words, there was a premise that the strength of the material could be understood from the atomic arrangement and elasticity theory. However, recent studies have reported that the strength characteristics of materials change significantly due to external influences such as light and an electric field. Therefore, Professor Nakamura notes, “it is becoming more and more accepted that other viewpoints must be added to the theory of material strength which include the motion of electrons and holes that are smaller than atoms.”

    “This study reaffirms the quantum-level effect on the strength of such materials. In this respect, it can be said that this research has achieved one milestone in the paradigm shift in the field of material strength that is currently occurring.”

    Dr. Xufei Fang adds: “Now that the creation of devices on the true nanoscale is becoming a reality, the impact of light on the structural strength of various inorganic semiconductors is an issue to be considered.”

    See the full article here.

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Nagoya University [名古屋大学; Nagoya daigaku](JP), is a Japanese national university located in Chikusa-ku, Nagoya. It is the last Imperial University in Japan, one of the Designated National University and selected as a Top Type university of Top Global University Project by the Japanese government. It is the 3rd highest ranked higher education institution in Japan (72nd worldwide).

    The University is the birthplace of the Sakata School of physics and the Hirata School of chemistry. As of 2014, six Nobel Prize winners have been associated with Nagoya University, the third most in Japan and Asia behind Kyoto University [京都大学, Kyōto daigaku](JP) and the U Tokyo [(東京大学] (JP).

    Nagoya University traces its roots back to 1871 when it was a temporary medical school. In 1939 it became Nagoya Imperial University [名古屋帝国大学]. In 1947 it was renamed Nagoya University [名古屋大学], and became a Japanese national university. In 2014, according to the reform measures of the Ministry of Education, Culture, Sports, Science and Technology, all Japanese national universities became National University Corporation [国立大学法人]. The university has a profound tradition of physics and chemistry. Many world-class scientific research achievements include Sakata model, PMNS matrix, Okazaki fragment, Noyori asymmetric hydrogenation, and Blue LED were born in Nagoya University.

    In the 20th century, NU’s Kuno Yasu and Katsunuma Seizō were nominated for the Nobel Prize in Physiology or Medicine, Yoshio Ohnuki was nominated for the Nobel Prize in Physics. In the 21st century, NU peoples account for half of the total number of Japanese Nobel Prize winners (up to 2014). Among the six winners of the Nobel Prize in Chemistry and the Physics, there are three professors and five alumni. The number of winners is the third among Japanese universities. In addition, the team under Professor Morishima Kunihiro participated in the Scanpyramids project by using special nuclear emulsion plates. This led to the discovery in 2017 of new chambers in the great pyramid.

    In March 2012, Nagoya University played host to the International Symposium on Innovative Nanobiodevices. Three years later, NU was selected as one of the five champion universities for gender equality by the United Nations Entity for Gender Equality and the Empowerment of Women.

    In March 2018, Nagoya University was selected as one of top five Designated National University Corporation [指定国立大学法人]. In order to become the largest national higher education corporation in Japan, the Tokai National Higher Education and Research System [国立大学法人東海国立大学機構] established by integrating with Gifu University in April 2020, both are major universities in Central Japan.

     
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