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  • richardmitnick 1:47 pm on February 21, 2020 Permalink | Reply
    Tags: "Otago physicists grab individual atoms in ground-breaking experiment", , , Laser Technology, , , The experiment improves on current knowledge by offering a previously unseen view into the microscopic world surprising researchers with the results., The University of Otago, Trapping and cooling of three atoms to a temperature of about a millionth of a Kelvin using highly focused laser beams in a hyper-evacuated (vacuum) chamber.   

    From The University of Otago, NZ: “Otago physicists grab individual atoms in ground-breaking experiment” 


    From The University of Otago

    20 February 2020

    Associate Professor Mikkel Andersen
    Department of Physics
    University of Otago
    Tel +64 3 479 7805
    Email mikkel.andersen@otago.ac.nz

    Mark Hathaway
    Senior Communications Adviser
    University of Otago
    Mob +64 21 279 5016
    Email mark.hathaway@otago.ac.nz

    LASER-cooled atom cloud viewed through microscope camera.

    In a first for quantum physics, University of Otago researchers have “held” individual atoms in place and observed previously unseen complex atomic interactions.

    A myriad of equipment including lasers, mirrors, a vacuum chamber, and microscopes assembled in Otago’s Department of Physics, plus a lot of time, energy, and expertise, have provided the ingredients to investigate this quantum process, which until now was only understood through statistical averaging from experiments involving large numbers of atoms.

    The experiment improves on current knowledge by offering a previously unseen view into the microscopic world, surprising researchers with the results.

    “Our method involves the individual trapping and cooling of three atoms to a temperature of about a millionth of a Kelvin using highly focused laser beams in a hyper-evacuated (vacuum) chamber, around the size of a toaster. We slowly combine the traps containing the atoms to produce controlled interactions that we measure,” says Associate Professor Mikkel F. Andersen of Otago’s Department of Physics.

    Mikkel Andersen (left) and Marvin Weyland in the physics lab.

    When the three atoms approach each other, two form a molecule, and all receive a kick from the energy released in the process. A microscope camera allows the process to be magnified and viewed.

    “Two atoms alone can’t form a molecule, it takes at least three to do chemistry. Our work is the first time this basic process has been studied in isolation, and it turns out that it gave several surprising results that were not expected from previous measurement in large clouds of atoms,” says Postdoctoral Researcher Marvin Weyland, who spearheaded the experiment.

    For example, the researchers were able to see the exact outcome of individual processes, and observed a new process where two of the atoms leave the experiment together. Until now, this level of detail has been impossible to observe in experiments with many atoms.

    “By working at this molecular level, we now know more about how atoms collide and react with one another. With development, this technique could provide a way to build and control single molecules of particular chemicals,” Weyland adds.

    Associate Professor Andersen admits the technique and level of detail can be difficult to comprehend to those outside the world of quantum physics, however he believes the applications of this science will be useful in development of future quantum technologies that might impact society as much as earlier quantum technologies that enabled modern computers and the Internet.

    “Research on being able to build on a smaller and smaller scale has powered much of the technological development over the past decades. For example, it is the sole reason that today’s cellphones have more computing power than the supercomputers of the 1980s. Our research tries to pave the way for being able to build at the very smallest scale possible, namely the atomic scale, and I am thrilled to see how our discoveries will influence technological advancements in the future,” Associate Professor Andersen says.

    The experiment findings [Physical Review Letters] showed that it took much longer than expected to form a molecule compared with other experiments and theoretical calculations, which currently are insufficient to explain this phenomenon. While the researchers suggest mechanisms which may explain the discrepancy, they highlight a need for further theoretical developments in this area of experimental quantum mechanics.

    This completely New Zealand-based research was primarily carried out by members of the University of Otago’s Department of Physics, with assistance from theoretical physicists at Massey University.

    See the full article here.


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    The University of Otago, founded in 1869 by an ordinance of the Otago Provincial Council, is New Zealand’s oldest university. The new University was given 100,000 acres of pastoral land as an endowment and authorised to grant degrees in Arts, Medicine, Law and Music.

    The University opened in July 1871 with a staff of just three Professors, one to teach Classics and English Language and Literature, another having responsibility for Mathematics and Natural Philosophy, and the third to cover Mental and Moral Philosophy and Political Economy. The following year a Professor of Natural Science joined the staff. With a further endowment provided in 1872, the syllabus was widened and new lectureships established: lectures in Law started in 1873, and in 1875 courses began in Medicine. Lectures in Mining were given from 1872, and in 1878 a School of Mines was established.

    The University was originally housed in a building (later the Stock Exchange) on the site of John Wickliffe House in Princes Street but it moved to its present site with the completion of the northern parts of the Clocktower and Geology buildings in 1878 and 1879.

    The School of Dentistry was founded in 1907 and the School of Home Science (later Consumer and Applied Sciences) in 1911. Teaching in Accountancy and Commerce subjects began in 1912. Various new chairs and lectureships were established in the years between the two world wars, and in 1946 teaching began in the Faculty of Theology. The School of Physical Education was opened in 1947.

    A federal University of New Zealand was established by statute in 1870 and became the examining and degree-granting body for all New Zealand university institutions until 1961. The University of Otago had conferred just one Bachelor of Arts degree, on Mr Alexander Watt Williamson, when in 1874 it became an affiliated college of the University of New Zealand.

    In 1961 the University of New Zealand was disestablished, and the power to confer degrees was restored to the University of Otago by the University of Otago Amendment Act 1961.

    Since 1961, when its roll was about 3,000, the University has expanded considerably (in 2016 there were over 20,000 students enrolled) and has broadened its range of qualifications to include undergraduate programmes in Surveying, Pharmacy, Medical Laboratory Science, Teacher Education, Physiotherapy, Applied Science, Dental Technology, Radiation Therapy, Dental Hygiene and Dental Therapy (now combined in an Oral Health programme), Biomedical Sciences, Social Work, and Performing Arts, as well as specialised postgraduate programmes in a variety of disciplines.

    Although the University’s main campus is in Dunedin, it also has Health Sciences campuses in Christchurch (University of Otago, Christchurch) and Wellington (University of Otago, Wellington) (established in 1972 and 1977 respectively), an information and teaching centre in central Auckland (1996), and an information office in Wellington (2001).

    The Dunedin College of Education merged with the University on 1 January 2007, and this added a further campus in Invercargill.

  • richardmitnick 9:13 am on February 21, 2020 Permalink | Reply
    Tags: , , , , HB11 Energy, Laser Technology, Laser-driven technique for creating fusion energy.,   

    From University of New South Wales: “Pioneering technology promises unlimited, clean and safe energy” 

    U NSW bloc

    From University of New South Wales

    21 Feb 2020
    Yolande Hutchinson
    UNSW Sydney External Relations
    0420 845 023

    Dr Warren McKenzie
    HB11 Energy
    0400 059 509

    Professor Heinrich Hora
    UNSW Physics
    0414 471 424

    A UNSW spin-out company has secured patents for its ground-breaking approach to energy generation.

    HB11 Energy, has been granted patents for its laser-driven technique for creating fusion energy. Picture: Shutterstock

    UNSW Sydney spin-out company, HB11 Energy, has been granted patents for its laser-driven technique for creating fusion energy. Unlike earlier methods, the technique is completely safe as it does not rely on radioactive fuel and leaves no toxic radioactive waste.

    HB11 Energy secured its intellectual property rights in Japan last week, following recent grants in China and the USA.

    Conceived by UNSW Emeritus Professor of theoretical physics Heinrich Hora, HB11 Energy’s concept differs radically from other experimental fusion projects.

    “After investigating a laser-boron fusion approach for over four decades at UNSW, I am thrilled that this pioneering approach has now received patents in three countries,” Professor Hora said.

    “These granted patents represent the eve of HB11 Energy’s seed-stage fundraising campaign that will establish Australia’s first commercial fusion company, and the world’s only approach focused on the safe hydrogen – boron reaction using lasers.”

    The preferred fusion approach employed by most fusion groups is to heat Deuterium-Tritium fuel well beyond the temperature of the sun (or almost 15 million degrees Celsius). Rather than heating the fuel, HB11’s hydrogen-boron fusion is achieved using two powerful lasers whose pulses apply precise non-linear forces to compress the nuclei together.

    “Tritium is very rare, expensive, radioactive and difficult to store. Fusion reactions employing Deuterium-Tritium also shed harmful neutrons and create radioactive waste which needs to be disposed of safely. I have long favored the combination of cheap and abundant hydrogen H and boron B-11. The fusion of these elements does not primarily produce neutrons and is the ideal fuel combination,” Professor Hora said.

    Most other sources of power production, such as coal, gas and nuclear, rely on heating liquids like water to drive turbines. In contrast, the energy generated by hydrogen-boron fusion converts directly into electricity allowing for much smaller and simpler generators.

    The two-laser approach needed for HB11 Energy’s hydrogen-boron fusion only became possible recently thanks to advances in laser technology that won the 2018 Nobel Prize in Physics.

    Schematic of a hydrogen-boron fusion reactor.

    Hora’s reactor design is deceptively simple: a largely empty metal sphere, where a modestly sized HB11 fuel pellet is held in the center, with apertures on different sides for the two lasers. One laser establishes the magnetic containment field for the plasma and the second laser triggers the ‘avalanche’ fusion chain reaction.

    The alpha particles generated by the reaction would create an electrical flow that can be channeled almost directly into an existing power grid with no need for a heat exchanger or steam turbine generator.

    “The clean and absolutely safe reactor can be placed within densely populated areas, with no possibility of a catastrophic meltdown such as that which has been seen with nuclear fission reactors,” Professor Hora added.

    With experiments and simulations measuring a laser-initiated chain reaction creating one billion-fold higher reaction rates than predicted (under thermal equilibrium conditions), HB11 Energy stands a high chance of reaching the goal of ‘net-energy gain’ well ahead of other groups.

    “HB11 Energy’s approach could be the only way to achieve very low carbon emissions by 2050. As we aren’t trying to heat fuels to impossibly high temperatures, we are sidestepping all of the scientific challenges that have held fusion energy back for more than half a century,” Dr Warren McKenzie, Managing Director of HB11 Energy, said.

    “This means our development roadmap will be much faster and cheaper than any other fusion approach,” Dr McKenzie added.

    See the full article here .


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    U NSW Campus

    Welcome to UNSW Australia (The University of New South Wales), one of Australia’s leading research and teaching universities. At UNSW, we take pride in the broad range and high quality of our teaching programs. Our teaching gains strength and currency from our research activities, strong industry links and our international nature; UNSW has a strong regional and global engagement.

    In developing new ideas and promoting lasting knowledge we are creating an academic environment where outstanding students and scholars from around the world can be inspired to excel in their programs of study and research. Partnerships with both local and global communities allow UNSW to share knowledge, debate and research outcomes. UNSW’s public events include concert performances, open days and public forums on issues such as the environment, healthcare and global politics. We encourage you to explore the UNSW website so you can find out more about what we do.

      • richardmitnick 2:40 pm on February 23, 2020 Permalink | Reply

        Many people could not find this article. I had over 2000 views on the article in the blog. But not one signed up to receive the blog. I notified UNSW of the problem.


    • Mark Peak 10:11 am on February 24, 2020 Permalink | Reply

      I’m happy to receive your blog. There did not appear to be link to request it. I am very interested in seeing the advances in more environmentally friendly forms of energy and being kept abreast of what is discovered and can be made available globally.


      • richardmitnick 10:43 am on February 24, 2020 Permalink | Reply

        Mark- Thank you so very much for taking the blog. The events around this article are very strange. Apparently somehow the original article disappeared even though I found a copy. I am in the U.S. but for my blog I follow a lot of universities and institutions in Australia, which as a country is a hotbed of Basic and Applied Scientific Research, just up my alley. UNSW is a very important center for research. I generally do about ten blog posts per day and get around 250 views per day. For this post from UNSW I have received over 3,000 views. I did write to UNSW to let them know about this set of events. I am sure I am not the only person who notified the university. Again, thanks for your interest and your comment.


  • richardmitnick 6:16 pm on February 18, 2020 Permalink | Reply
    Tags: "Researchers combine lasers and terahertz waves in camera that sees 'unseen' detail", , Laser Technology, , , University of Sussex   

    From University of Sussex via phys.org: “Researchers combine lasers and terahertz waves in camera that sees ‘unseen’ detail” 

    From University of Sussex



    February 18, 2020

    The time-resolved nonlinear ghost imaging camera uses a nonlinear crystal to convert standard laser light to terahertz patterns, allowing the reconstruction of complex samples using a single terahertz pixel. Credit: University of Sussex

    A team of physicists at the University of Sussex has successfully developed the first nonlinear camera capable of capturing high-resolution images of the interior of solid objects using terahertz (THz) radiation.

    Led by Professor Marco Peccianti of the Emergent Photonics (EPic) Lab, Luana Olivieri, Dr. Juan S. Totero Gongora and a team of research students built a new type of THz camera capable of detecting THz electromagnetic waves with unprecedented accuracy.

    Images produced using THz radiation are called ‘hyperspectral’ because the image consists of pixels, each one containing the electromagnetic signature of the object in that point.

    Lying between microwaves and infrared in the electromagnetic spectrum, THz radiation easily penetrates materials like paper, clothes and plastic in the same way X-rays do, but without being harmful. It is safe to use with even the most delicate biological samples. THz imaging makes it possible to ‘see’ the molecular composition of objects and distinguish between different materials—such as sugar and cocaine, for example.

    Explaining the significance of their achievement, Prof Peccianti said: “The core challenge in THz cameras is not about collecting an image, but it is about preserving the objects spectral fingerprint that can be easily corrupted by your technique. This is where the importance of our achievement lies. The fingerprint of all the details of the image is preserved in such a way that we can investigate the nature of the object in full detail. ”

    Artistic rendering of the terahertz field transmitted by an abstract object. Credit: University of Sussex

    Until now, cameras capable of capturing a hyperspectral image preserving all the fine details revealed by THz radiation had not been considered possible.

    The EPic Lab team used a single-pixel camera to image sample objects with patterns of THz light. The prototype they built can detect how the object alters different patterns of THz light. By combining this information with the shape of each original pattern, the camera reveals the image of an object as well as its chemical composition.

    Sources of THz radiation are very faint and hyperspectral imaging had, until now, limited fidelity. To overcome this, The Sussex team shone a standard laser onto a unique non-linear material capable of converting visible light to THz. The prototype camera creates THz electromagnetic waves very close to the sample, similar to how a microscope works. As THz waves can travel right through an object without affecting it, the resulting images reveal the shape and composition of objects in three dimensions.

    Dr. Totero Gongora said: “This is a major step forward because we have demonstrated that all the possibilities explored in our previous theoretical research are not only feasible, but our camera works even better than we expected. While building our device, we discovered several ways to optimise the imaging process and now the technology is stable and works well. The next phase of our research will be in speeding up the image reconstruction process and taking us closer to applying THz cameras to real-world applications; like airport security, intelligent car sensors, quality control in manufacturing and even scanners to detect health problems like skin cancer.”

    Science paper:
    Luana Olivieri et al. Hyperspectral terahertz microscopy via nonlinear ghost imaging, Optica (2020)

    See the full article here .


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    About Science X in 100 words

    Science X™ is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
    Mission 12 reasons for reading daily news on Science X Organization Key editors and writersinclude 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.


    The University of Sussex is a public research university located in Falmer, Sussex, England. Its campus is surrounded by the South Downs National Park and it is a short distance away from central Brighton. The University received its Royal Charter in August 1961, the first of the plate glass university generation, and was a founding member of the 1994 Group of research-intensive universities.

    More than a third of its students are enrolled in postgraduate programs and approximately a third of staff are from outside the United Kingdom. Sussex has a diverse community of over 17,000 students, with around one in three being foreign students, and over 1000 academics, representing over 140 different nationalities. The annual income of the institution for 2016–17 was £286.1 million with an expenditure of £270.4 million. In 2017, over 32,000 students applied to the University of Sussex, with around 5,000 joining the institution.

    The Times Higher Education World University Rankings 2018 placed Sussex 147th in the world overall, 39th in the world for Social Sciences and 49th globally for Business and Law studies. Sussex is particularly known for its Humanities and Social Sciences departments, with its Development studies program being placed at number 1 globally in the QS World University Ranking.

    Sussex counts 5 Nobel Prize winners, 15 Fellows of the Royal Society, 9 Fellows of the British Academy, 24 fellows of the Academy of Social Sciences and a winner of the Crafoord Prize among its faculty. By 2011, many of its faculty members had also received the Royal Society of Literature Prize, the Order of the British Empire and the Bancroft Prize. Alumni include heads of states, diplomats, politicians, eminent scientists and activists.

  • richardmitnick 1:17 pm on February 17, 2020 Permalink | Reply
    Tags: "Scientists unlock low-cost material to shape light for industry", , , Faraday rotators, Laser Technology, , Manipulate light in a range of devices across industry and science by altering a fundamental property of light – its polarization.,   

    From University of Sydney: “Scientists unlock low-cost material to shape light for industry” 

    U Sidney bloc

    From University of Sydney

    17 February 2020

    Marcus Strom
    Science Media Adviser
    Phone+ 61 2 8627 6433
    Mobile +61 423 982 485

    Perovskite crystals adapted for use as Faraday rotators.

    In the lab (from left): Dr Girish Lakhwani, Dr Stefano Bernardi and Dr Randy Sabatini. Photo: Stefanie Zingsheim/University of Sydney.

    Image above: The polarisation of transmitted light is rotated by a crystal immersed in a magnetic field (top). The perovskite crystal (bottom right) rotates light very effectively, due to the atomic configuration of its crystal structure (bottom left).

    Researchers in Australia have found a way to manipulate laser light at a fraction of the cost of current technology.

    The discovery, published in Advanced Science, could help drive down costs in industries as diverse as telecommunications, medical diagnostics and consumer optoelectronics.

    The research team, led by Dr Girish Lakhwani from the University of Sydney Nano Institute and School of Chemistry, has used inexpensive crystals, known as perovskites, to make Faraday rotators. These manipulate light in a range of devices across industry and science by altering a fundamental property of light – its polarisation. This gives scientists and engineers the ability to stabilise, block or steer light on demand.

    Faraday rotators are used at the source of broadband and other communication technologies, blocking reflected light that would otherwise destabilise lasers and amplifiers. They are used in optical switches and fibre-optic sensors as well.

    Dr Lakhwani said: “The global optical switches market alone is worth more than $US4.5 billion and is growing. The major competitive advantage perovskites have over current Faraday isolators is the low cost of material and ease of processing that would allow for scalability.”

    To date, the industry standard for Faraday rotators has been terbium-based garnets. Dr Lakhwani and colleagues at the Australian Research Centre of Excellence in Exciton Science have used lead-halide perovskites, which could prove a less expensive alternative.

    Dr Lakhwani said: “Development and uptake of our technology could be aided by the excellent positioning of Australia within the Asia-Pacific region, which is growing rapidly due to increasing investments in its high-speed communication infrastructure.”

    Adapting perovskites

    The lead-halide perovskites used by the Lakhwani group are a class of materials that have been gaining a lot of traction in the scientific community, thanks to a combination of excellent optical properties and low production costs.

    “Interest in perovskites really started with solar cells,” said Dr Randy Sabatini, a postdoctoral researcher leading the project in the Lakhwani group.

    “They are efficient and much less expensive than traditional silicon cells, which are made using a costly process known as the Czochralski or Cz method. Now, we’re looking at another application, Faraday rotation, where the commercial standards are also made using the Cz method. Just like in solar cells, it seems like perovskites might be able to compete here as well.”

    In this paper, the team shows that the performance of perovskites can rival that of commercial standards for certain colours within the visible spectrum.

    Collaboration is key

    “As part of the ARC Centre of Excellence in Exciton Science (ACEx), we benefitted from the exchange of ideas through this high-calibre centre,” Dr Lakhwani said. Collaborators included the ACEx groups of Professor Udo Bach at Monash University and Dr Asaph Widmer-Cooper at Sydney, as well as the Professor Anita Ho-Baillie group at UNSW. Professor Ho-Baillie has since joined the University of Sydney as the inaugural John Hooke Chair of Nanoscience.

    “We’ve been looking into Faraday rotation for quite some time,” Dr Lakhwani said. “It’s very difficult to find solution-processed materials that rotate light polarisation effectively. Based on their structure, we were hoping that perovskites would be good, but they really surpassed our expectations.”

    Looking ahead, the search for other perovskite materials should be aided by modelling.

    “For most materials, the classical theory used to predict Faraday rotation performs very poorly,” said Dr Stefano Bernardi, a postdoctoral researcher in the Widmer-Cooper group at the University of Sydney. “However, for perovskites the agreement is surprisingly good, so we hope that this will allow us to create even better crystals.”

    The team has also performed thermal simulations to understand how a real device would function. However, there is still work to be done to make commercial application a reality.

    “We plan on continuing to improve the crystal transparency and growth reproducibility,” said Chwenhaw Liao, from UNSW. “However, we’re very happy with the initial progress and are optimistic for the future.”


    This work was supported by the Australian Research Council Centre of Excellence in Exciton Science.

    See the full article here .


    Please help promote STEM in your local schools.

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    U Sidney campus

    University of Sydney
    Our founding principle as Australia’s first university was that we would be a modern and progressive institution. It’s an ideal we still hold dear today.

    When Charles William Wentworth proposed the idea of Australia’s first university in 1850, he imagined “the opportunity for the child of every class to become great and useful in the destinies of this country”.

    We’ve stayed true to that original value and purpose by promoting inclusion and diversity for the past 160 years.

    It’s the reason that, as early as 1881, we admitted women on an equal footing to male students. Oxford University didn’t follow suit until 30 years later, and Jesus College at Cambridge University did not begin admitting female students until 1974.

    It’s also why, from the very start, talented students of all backgrounds were given the chance to access further education through bursaries and scholarships.

    Today we offer hundreds of scholarships to support and encourage talented students, and a range of grants and bursaries to those who need a financial helping hand.

  • richardmitnick 4:26 pm on February 11, 2020 Permalink | Reply
    Tags: "Using sound and light to generate ultra-fast data transfer", , Laser Technology,   

    From University of Leeds: “Using sound and light to generate ultra-fast data transfer” 

    U Leeds bloc

    From University of Leeds

    February 11, 2020
    David Lewis
    +44(0)113 343 2049

    The quantum cascade laser, on its mounting, being held by a set of tweezers

    Researchers have made a breakthrough in the control of terahertz quantum cascade lasers, which could lead to the transmission of data at the rate of 100 gigabits per second.

    That ultra-fast data transfer would be around one thousand times quicker than a fast Ethernet operating at 100 megabits a second.

    What distinguishes terahertz quantum cascade lasers from other lasers is the fact they emit light in the terahertz range of the electromagnetic spectrum. They have applications in the field of spectroscopy where they are used in chemical analysis.

    The lasers could also eventually provide ultra-fast, short-hop wireless links where large datasets have to be transferred across hospital campuses or between research facilities on universities – or in satellite communications.

    To be able to send data at these increased speeds, the lasers need to be modulated very rapidly: switching on and off or pulsing about 100 billion times every second.

    Engineers and scientists have so far failed to develop a way of achieving this.

    A research team of academics from the University of Leeds and University of Nottingham believes its has found a way of delivering ultra- fast modulation, by combining the power of acoustic and light waves. The findings are published today in Nature Communications.

    John Cunningham, Professor of Nanoelectronics in the School of Electronic and Electrical Engineering at Leeds, said: “This is exciting research. At the moment, the system for modulating a quantum cascade laser is electrically driven – but that system has limitations.

    “Ironically, the same electronics that delivers the modulation usually puts a brake on the speed of the modulation. The mechanism we are developing relies instead on acoustic waves.”

    A quantum cascade laser is very efficient. As an electron passes through the optical component of the laser, it goes through a series of “quantum wells” where the energy level of the electron drops and a photon or pulse of light energy is emitted. One electron is capable of emitting multiple photons. It is this process that is controlled during the modulation.

    Instead of using external electronics, the researchers used acoustic waves to vibrate the quantum wells inside the quantum cascade laser. The acoustic waves were generated by the impact of a pulse from another laser onto an aluminium film. This caused the film to expand and contract, sending a mechanical wave through the quantum cascade laser.

    Tony Kent, Professor of Physics at Nottingham, said “Essentially, what we did was use the acoustic wave to shake the intricate electronic states inside the quantum cascade laser. We could then see that its terahertz light output was being altered by the acoustic wave.”

    Professor Cunningham added: “We did not reach a situation where we could stop and start the flow completely, but we were able to control the light output by a few percent, which is a great start. We believe that with further refinement, we will be able to develop a new mechanism for complete control of the photon emissions from the laser, and perhaps even integrate structures generating sound with the terahertz laser, so that no external sound source is needed.”

    Professor Kent said: “This result opens a new area for physics and engineering to come together in the exploration of the interaction of terahertz sound and light waves, which could have real technological applications.”

    See the full article here.


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    U Leeds Campus

    The University of Leeds, established in 1904, is one of the largest higher education institutions in the UK. We are a world top 100 university and are renowned globally for the quality of our teaching and research. The strength of our academic expertise combined with the breadth of disciplines we cover, provides a wealth of opportunities and has real impact on the world in cultural, economic and societal ways. The University strives to achieve academic excellence within an ethical framework informed by our values of integrity, equality and inclusion, community and professionalism.

  • richardmitnick 12:14 am on February 8, 2020 Permalink | Reply
    Tags: "A Quantum of Solid", , , Cooling a levitated nanoparticle to its motional quantum groundstate., Laser Technology, , New macroscopic quantum states involving large masses should become possible., Physicists do something very cool, , , Universität Wien   

    From Universität Wien: “A Quantum of Solid” 

    From Universität Wien

    30. January 2020
    Scientific contact
    Univ.-Prof. Dr. Markus Aspelmeyer
    Quantenoptik, Quantennanophysik und Quanteninformation
    Universität Wien
    1090 – Wien, Boltzmanngasse 5
    +43-1-4277-725 31

    Dr. Uros Delic, BSc MSc
    Fakultät für Physik
    Universität Wien
    1090 – Wien, Boltzmanngasse 5

    Further inquiry note
    Mag. Alexandra Frey
    Pressebüro und stv. Pressesprecherin
    Universität Wien
    1010 – Wien, Universitätsring 1
    +43-1-4277-175 33
    +43-664-60277-175 33

    Scientists from Vienna, Kahan Dare (left) and Manuel Reisenbauer (right) working on the experiment that cooled a levitated nanoparticle to its motional quantum groundstate. (© Lorenzo Magrini, Yuriy Coroli/Universität Wien)

    Scientist from Vienna working on the experiment that cooled a levitated nanoparticle to its motional quantum groundstate. (© Lorenzo Magrini, Yuriy Coroli/Universität Wien)

    Researchers cooled a levitated nanoparticle to the quantum groundstate for the first time. This work was made possible by the recent breakthrough application of coherent scattering in the field of cavity optomechanics. (© Lorenzo Magrini, Yuriy Coroli/Universität Wien)

    Researchers in Austria use lasers to levitate and cool a glass nanoparticle into the quantum regime. Although it is trapped in a room temperature environment, the particle’s motion is solely governed by the laws of quantum physics. The team of scientists from the Universität Wien, the Austrian Academy of Sciences and the Massachusetts Institute of Technology (MIT) published their new study in the journal Science.

    It is well known that quantum properties of individual atoms can be controlled and manipulated by laser light. Even large clouds of hundreds of millions of atoms can be pushed into the quantum regime, giving rise to macroscopic quantum states of matter such as quantum gases or Bose-Einstein condensates, which nowadays are also widely used in quantum technologies. An exciting next step is to extend this level of quantum control to solid state objects. In contrast to atomic clouds, the density of a solid is a billion times higher and all atoms are bound to move together along the object’s center of mass. In that way, new macroscopic quantum states involving large masses should become possible.

    However, entering this new regime is not at all a straightforward endeavour. A first step for achieving such quantum control is to isolate the object under investigation from influences of the environment and to remove all thermal energy – by cooling it down to temperatures very close to absolute zero (-273.15 °C) such that quantum mechanics dominates the particle’s motion. To show this the researchers chose to experiment with a glass bead approximately a thousand times smaller than a typical grain of sand and containing a few hundred million atoms. Isolation from the environment is achieved by optically trapping the particle in a tightly focused laser beam in high vacuum, a trick that was originally introduced by Nobel laureate Arthur Ashkin many decades ago and that is also used for isolating atoms. “The real challenge is for us to cool the particle motion into its quantum ground state. Laser cooling via atomic transitions is well established and a natural choice for atoms, but it does not work for solids”, says lead-author Uros Delic from the Universität Wien.

    For this reason, the team has been working on implementing a laser-cooling method that was proposed by Austrian physicist Helmut Ritsch at the University of Innsbruck and, independently, by study co-author Vladan Vuletic and Nobel laureate Steven Chu. They had recently announced a first demonstration of the working principle, “cavity cooling by coherent scattering”, however they were still limited to operating far away from the quantum regime. “We have upgraded our experiment and are now able not only to remove more background gas but also to send in more photons for cooling”, says Delic. In that way, the motion of the glass bead can be cooled straight into the quantum regime. “It is funny to think about this: the surface of our glass bead is extremely hot, around 300°C, because the laser heats up the electrons in the material. But the motion of the center of mass of the particle is ultra-cold, around 0.00001°C away from absolute zero, and we can show that the hot particle moves in a quantum way.”

    The researchers are excited about the prospects of their work. The quantum motion of solids has also been investigated by other groups all around the world, along with the Vienna team. Thus far, experimental systems were comprised of nano- and micromechanical resonators, in essence drums or diving boards that are clamped to a rigid support structure. “Optical levitation brings in much more freedom: by changing the optical trap – or even switching it off – we can manipulate the nanoparticle motion in completely new ways”, says Nikolai Kiesel, co-author and Assistant Professor at the Universität Wien. Several schemes along these lines have been proposed, amongst others by Austrian-based physicists Oriol Romero-Isart and Peter Zoller at Innsbruck, and may now become possible. For example, in combination with the newly achieved motional ground state the authors expect that this opens new opportunities for unprecedented sensing performance, the study of fundamental processes of heat engines in the quantum regime, as well as the study of quantum phenomena involving large masses. “A decade ago we started this experiment motivated by the prospect of a new category of quantum experiments. We finally have opened the door to this regime.”

    See the full article here .


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    Universität Wien Campus

    Universität Wien is a public university located in Vienna, Austria. It was founded by Duke Rudolph IV in 1365 and is the oldest university in the German-speaking world. With its long and rich history, the University of Vienna has developed into one of the largest universities in Europe, and also one of the most renowned, especially in the Humanities. It is associated with 20 Nobel prize winners and has been the academic home to many scholars of historical as well as of academic importance.

  • richardmitnick 12:14 pm on January 31, 2020 Permalink | Reply
    Tags: "Researchers discover a new way to control infrared light", A phase-change material's magic occurs in the chemical bonds that tie its atoms together., , Currently optical chips lenses and filters must be rebuilt from scratch each time a change is required., , GSST- Using a new class of phase-change material containing the elements germanium; antimony; selenium; and tellurium., , Laser Technology, , , Recently the laboratory obtained a combinatorial sputtering chamber — a state-of-the-art machine that allows researchers to create custom materials out of individual elements., The potential uses for GSST are vast and an ultimate goal for the team is to design reconfigurable optical chips lenses and filters., Using phase-change materials instead of moving parts.   

    From MIT News: “Researchers discover a new way to control infrared light” 

    MIT News

    From MIT News

    The new method could impact devices used in imaging, machine learning, and more.

    January 30, 2020
    Anne McGovern | Lincoln Laboratory

    This 8-inch wafer contains phase-change pixels that can be controlled to modulate light. Researchers are studying the properties and behaviors of the pixels to inform the creation of future devices that use phase-change materials. Image: Nicole Fandel.

    In the 1950s, the field of electronics began to change when the transistor replaced vacuum tubes in computers. The change, which entailed replacing large and slow components with small and fast ones, was a catalyst for the enduring trend of miniaturization in computer design. No such revolution has yet hit the field of infrared optics, which remains reliant on bulky moving parts that preclude building small systems.

    However, a team of researchers at MIT Lincoln Laboratory, together with Professor Juejun Hu and graduate students from MIT’s Department of Materials Science and Engineering, is devising a way to control infrared light by using phase-change materials instead of moving parts. These materials have the ability to change their optical properties when energy is added to them.

    “There are multiple possible ways where this material can enable new photonic devices that impact people’s lives,” says Hu. “For example, it can be useful for energy-efficient optical switches, which can improve network speed and reduce power consumption of internet data centers. It can enable reconfigurable meta-optical devices, such as compact, flat infrared zoom lenses without mechanical moving parts. It can also lead to new computing systems, which can make machine learning faster and more power-efficient compared to current solutions.”

    A fundamental property of phase-change materials is that they can change how fast light travels through them (the refractive index). “There are already ways to modulate light using a refractive index change, but phase-change materials can change almost 1,000 times better,” says Jeffrey Chou, a team member formerly in the laboratory’s Advanced Materials and Microsystems Group.

    The team successfully controlled infrared light in multiple systems by using a new class of phase-change material containing the elements germanium, antimony, selenium, and tellurium, collectively known as GSST. This work is discussed in a paper published in Nature Communications.

    A phase-change material’s magic occurs in the chemical bonds that tie its atoms together. In one phase state, the material is crystalline, with its atoms arranged in an organized pattern. This state can be changed by applying a short, high-temperature spike of thermal energy to the material, causing the bonds in the crystal to break down and then reform in a more random, or amorphous, pattern. To change the material back to the crystalline state, a long- and medium-temperature pulse of thermal energy is applied.

    “This changing of the chemical bonds allows for different optical properties to emerge, similar to the differences between coal (amorphous) and diamond (crystalline),” says Christopher Roberts, another Lincoln Laboratory member of the research team. “While both materials are mostly carbon, they have vastly different optical properties.”

    Currently, phase-change materials are used for industry applications, such as Blu-ray technology and rewritable DVDs, because their properties are useful for storing and erasing a large amount of information. But so far, no one has used them in infrared optics because they tend to be transparent in one state and opaque in the other. (Think of the diamond, which light can pass through, and coal, which light cannot penetrate.) If light cannot pass through one of the states, then that light cannot be adequately controlled for a range of uses; instead, a system would only be able to work like an on/off switch, allowing light to either pass through the material or not pass through at all.

    However, the research team found that that by adding the element selenium to the original material (called GST), the material’s absorption of infrared light in the crystalline phase decreased dramatically — in essence, changing it from an opaque coal-like material to a more transparent diamond-like one. What’s more, the large difference in the refractive index of the two states affects the propagation of light through them.

    “This change in refractive index, without introducing optical loss, allows for the design of devices that control infrared light without the need for mechanical parts,” Roberts says.

    As an example, imagine a laser beam that is pointing in one direction and needs to be changed to another. In current systems, a large mechanical gimbal would physically move a lens to steer the beam to another position. A thin-film lens made of GSST would be able change positions by electrically reprogramming the phase-change materials, enabling beam steering with no moving parts.

    The team has already tested the material successfully in a moving lens. They have also demonstrated its use in infrared hyperspectral imaging, which is used to analyze images for hidden objects or information, and in a fast optical shutter that was able to close in nanoseconds.

    The potential uses for GSST are vast, and an ultimate goal for the team is to design reconfigurable optical chips, lenses, and filters, which currently must be rebuilt from scratch each time a change is required. Once the team is ready to move the material beyond the research phase, it should be fairly easy to transition it into the commercial space. Because it’s already compatible with standard microelectronic fabrication processes, GSST components could be made at a low cost and in large numbers.

    Recently, the laboratory obtained a combinatorial sputtering chamber — a state-of-the-art machine that allows researchers to create custom materials out of individual elements. The team will use this chamber to further optimize the materials for improved reliability and switching speeds, as well as for low-power applications. They also plan to experiment with other materials that may prove useful in controlling visible light.

    The next steps for the team are to look closely into real-world applications of GSST and understand what those systems need in terms of power, size, switching speed, and optical contrast.

    “The impact [of this research] is twofold,” Hu says. “Phase-change materials offer a dramatically enhanced refractive index change compared to other physical effects — induced by electric field or temperature change, for instance — thereby enabling extremely compact reprogrammable optical devices and circuits. Our demonstration of bistate optical transparency in these materials is also significant in that we can now create high-performance infrared components with minimal optical loss.” The new material, Hu continues, is expected to open up an entirely new design space in the field of infrared optics.

    This research was supported with funding from the laboratory’s Technology Office and the U.S. Defense Advanced Research Projects Agency.

    See the full article here .

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    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.

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  • richardmitnick 2:45 pm on January 30, 2020 Permalink | Reply
    Tags: "An ultrafast microscope for the quantum world", An attosecond is a billionth of a billionth of a second., , From Max Planck Institute for Solid State Research, Laser Technology, , , Researchers need a high-speed camera that exposes each frame of an “electron video” for just a few hundred attoseconds., Scanning tunnelling microscope   

    From Max Planck Institute for Solid State Research: “An ultrafast microscope for the quantum world” 

    From Max Planck Institute for Solid State Research

    January 24, 2020

    Dr. Manish Garg
    Max Planck Institute for Solid State Research, Stuttgart
    +49 711 689-1639
    +49 711 689-1637

    Prof. Dr. Klaus Kern
    Max Planck Institute for Solid State Research, Stuttgart
    +49 711 689-1660

    Resolution taken to the extreme: Using a combination of ultrashort laser pulses (red) and a scanning tunnelling microscope, researchers at the Max Planck Institute for Solid State Research are filming processes in the quantum world. They focus the laser flashes on the tiny gap between the tip of the microscope and the sample surface, thus solving the tunneling process in which electrons (blue) overcome the gap between the tip and the sample. In this way, they achieve a temporal resolution of several hundred attoseconds when they image quantum processes such as an electronic wave packet (coloured wave) with atomic spatial resolution. © Dr. Christian Hackenberger

    The operation of components for future computers can now be filmed in HD quality, so to speak. Manish Garg and Klaus Kern, researchers at the Max Planck Institute for Solid State Research in Stuttgart, have developed a microscope for the extremely fast processes that take place on the quantum scale. This microscope – a sort of HD camera for the quantum world – allows the precise tracking of electron movements down to the individual atom. It should therefore provide useful insights when it comes to developing extremely fast and extremely small electronic components, for example.

    The processes taking place in the quantum world represent a challenge for even the most experienced of physicists. For example, the things taking place inside the increasingly powerful components of computers or smartphones not only happen extremely quickly but also within an ever-smaller space. When it comes to analysing these processes and optimising transistors, for example, videos of the electrons would be of great benefit to physicists. To achieve this, researchers need a high-speed camera that exposes each frame of this “electron video” for just a few hundred attoseconds. An attosecond is a billionth of a billionth of a second; in that time, light can only travel the length of a water molecule. For a number of years, physicists have used laser pulses of a sufficiently short length as an attosecond camera.

    In the past, however, an attosecond image delivered only a snapshot of an electron against what was essentially a blurred background. Now, thanks to the work of Klaus Kern, Director at the Max Planck Institute for Solid State Research, and Manish Garg, a scientist in Kern’s Department, researchers can now also identify precisely where the filmed electron is located down to the individual atom.

    Ultrashort laser pulses combined with a scanning tunnelling microscope.

    To do this, the two physicists use ultrashort laser pulses in conjunction with a scanning tunnelling microscope. The latter achieves atomic-scale resolution by scanning a surface with a tip that itself is ideally made up of just a single atom. Electrons tunnel between the tip and the surface – that is, they cross the intervening space even though they actually don’t have enough energy to do so. As the effectiveness of this tunnelling process depends strongly on the distance the electrons have to travel, it can be used to measure the space between the tip and a sample and therefore to depict even individual atoms and molecules on a surface. Until now, however, scanning tunnelling microscopes did not achieve sufficient temporal resolution to track electrons.

    “By combining a scanning tunnelling microscope with ultrafast pulses, it was easy to use the advantages of the two methods to compensate for their respective disadvantages,” says Manish Garg. The researchers fire these extremely short pulses of light at the microscope tip – which is positioned with atomic precision – to trigger the tunnelling process. As a result, this high-speed camera for the quantum world can now also achieve HD resolution.

    Paving the way for light-wave electronics, which is millions of times faster.

    With the new technique, physicists can now measure exactly where electrons are at a specific time down to the individual atom and to an accuracy of a few hundred attoseconds. For example, this can be used in molecules that have had an electron catapulted out of them by a high-energy pulse of light, leading the remaining negative charge carriers to rearrange themselves and possibly causing the molecule to enter into a chemical reaction with another molecule. “Filming electrons in molecules live, and on their natural spatial and temporal scale, is vital in order to understand chemical reactivity, for example, and the conversion of light energy within charged particles, such as electrons or ions,” says Klaus Kern, Director at the Max Planck Institute for Solid State Research.

    Moreover, the technique not only allows researchers to track the path of electrons through the processors and chips of the future, but can also lead to a dramatic acceleration of the charge carriers: “In today’s computers, electrons oscillate at a frequency of a billion hertz,” says Klaus Kern. “Using ultrashort light pulses, it may be possible to increase their frequency to a trillion hertz.” With this turbo booster for light waves, researchers could clear the way for light-wave electronics, which is millions of times faster than current computers. Therefore, the ultrafast microscope not only films processes in the quantum world, but also acts as the Director by interfering with these processes.

    Science paper:
    M. Garg et al, “Attosecond coherent manipulation of electrons in tunneling microscopy”

    See the full article here .

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    Stem Education Coalition

    The Max Planck Institute for Solid State Research (German: Max-Planck-Institut für Festkörperforschung) was founded in 1969 and is one of the 82 Max Planck Institutes of the Max Planck Society. It is located on a campus in Stuttgart, together with the Max Planck Institute for Intelligent Systems.

    Research at the Max Planck Institute for Solid State Research is focused on the physics and chemistry of condensed matter, including especially complex materials and nanoscale science. In both of these fields, electronic and ionic transport phenomena are of particular interest.

    MPG campus

    The Max Planck Society for the Advancement of Science (German: Max-Planck-Gesellschaft zur Förderung der Wissenschaften e. V.; abbreviated MPG) is a formally independent non-governmental and non-profit association of German research institutes founded in 1911 as the Kaiser Wilhelm Society and renamed the Max Planck Society in 1948 in honor of its former president, theoretical physicist Max Planck. The society is funded by the federal and state governments of Germany as well as other sources.

    According to its primary goal, the Max Planck Society supports fundamental research in the natural, life and social sciences, the arts and humanities in its 83 (as of January 2014)[2] Max Planck Institutes. The society has a total staff of approximately 17,000 permanent employees, including 5,470 scientists, plus around 4,600 non-tenured scientists and guests. Society budget for 2015 was about €1.7 billion.

    The Max Planck Institutes focus on excellence in research. The Max Planck Society has a world-leading reputation as a science and technology research organization, with 33 Nobel Prizes awarded to their scientists, and is generally regarded as the foremost basic research organization in Europe and the world. In 2013, the Nature Publishing Index placed the Max Planck institutes fifth worldwide in terms of research published in Nature journals (after Harvard, MIT, Stanford and the US NIH). In terms of total research volume (unweighted by citations or impact), the Max Planck Society is only outranked by the Chinese Academy of Sciences, the Russian Academy of Sciences and Harvard University. The Thomson Reuters-Science Watch website placed the Max Planck Society as the second leading research organization worldwide following Harvard University, in terms of the impact of the produced research over science fields.

  • richardmitnick 9:57 pm on January 27, 2020 Permalink | Reply
    Tags: "Method detects defects in 2D materials for future electronics sensors", , Dark field imaging-a technique in which extraneous light is filtered out so that defects shine through., Laser Technology, ,   

    From Pennsylvania State University: “Method detects defects in 2D materials for future electronics, sensors” 

    Penn State Bloc

    From Pennsylvania State University

    January 27, 2020
    Walt Mills

    A laser beam (yellow) reflects off a 2D material (orange) highlighting a grain boundary defect in the atomic lattice. Image: MRI/Penn State

    To further shrink electronic devices and to lower energy consumption, the semiconductor industry is interested in using 2D materials, but manufacturers need a quick and accurate method for detecting defects in these materials to determine if the material is suitable for device manufacture. Now a team of researchers has developed a technique to quickly and sensitively characterize defects in 2D materials.

    Two-dimensional materials are atomically thin, the most well-known being graphene, a single-atom-thick layer of carbon atoms.

    “People have struggled to make these 2D materials without defects,” said Mauricio Terrones, Verne M. Willaman Professor of Physics, Penn State. “That’s the ultimate goal. We want to have a 2D material on a four-inch wafer with at least an acceptable number of defects, but you want to evaluate it in a quick way.”

    The researchers’ — who represent Penn State, Northeastern University, Rice University and Universidade Federal de Minas Gerais in Brazil – solution is to use laser light combined with second harmonic generation, a phenomenon in which the frequency of the light shone on the material reflects at double the original frequency. They add dark field imaging, a technique in which extraneous light is filtered out so that defects shine through. According to the researchers, this is the first instance in which dark field imaging was used, and it provides three times the brightness of the standard bright field imaging method, making it possible to see types of defects previously invisible.

    “The localization and identification of defects with the commonly used bright field second harmonic generation is limited because of interference effects between different grains of 2D materials,” said Leandro Mallard, a senior author on a recent paper in Nano Letters and a professor at Universidade Federal de Minas Gerais. “In this work we have shown that by the use of dark field SHG we remove the interference effects and reveal the grain boundaries and edges of semiconducting 2D materials. Such a novel technique has good spatial resolution and can image large area samples that could be used to monitor the quality of the material produced in industrial scales.”

    Vincent H. Crespi, Distinguished Professor of Physics, Materials Science and Engineering, and Chemistry, Penn State, added, “Crystals are made of atoms, and so the defects within crystals — where atoms are misplaced — are also of atomic size.

    “Usually, powerful, expensive and slow experimental probes that do microscopy using beams of electrons are needed to discern such fine details in a material,” said Crespi. “Here, we use a fast and accessible optical method that pulls out just the signal that originates from the defect itself to rapidly and reliably find out how 2D materials are stitched together out of grains oriented in different ways.”

    Another coauthor compared the technique to finding a particular zero on a page full of zeroes.

    “In the dark field, all the zeroes are made invisible so that only the defective zero stands out,” said Yuanxi Wang, assistant research professor at Penn State’s Materials Research Institute.

    The semiconductor industry wants to have the ability to check for defects on the production line, but 2D materials will likely be used in sensors before they are used in electronics, according to Terrones. Because 2D materials are flexible and can be incorporated into very small spaces, they are good candidates for multiple sensors in a smartwatch or smartphone and the myriad of other places where small, flexible sensors are required.

    “The next step would be an improvement of the experimental setup to map zero dimension defects — atomic vacancies for instance — and also extend it to other 2D materials that host different electronic and structural properties,” said lead author Bruno Carvalho, a former visiting scholar in Terrones’ group,

    Other co-authors on the Nano Letters paper, are Kuzanori Fujisawa, Tianyi Zhang, Ethan Kahn, Ismail Bilgin, Pulickel Ajayan, Ana de Paula, Marcos Pimenta and Swastik Kar.

    The National Science Foundation, The Air Force Office of Scientific Research and various Brazilian funding agencies funded this work.

    See the full article here .


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    Penn State Campus

    About Penn State


    We teach students that the real measure of success is what you do to improve the lives of others, and they learn to be hard-working leaders with a global perspective. We conduct research to improve lives. We add millions to the economy through projects in our state and beyond. We help communities by sharing our faculty expertise and research.

    Penn State lives close by no matter where you are. Our campuses are located from one side of Pennsylvania to the other. Through Penn State World Campus, students can take courses and work toward degrees online from anywhere on the globe that has Internet service.

    We support students in many ways, including advising and counseling services for school and life; diversity and inclusion services; social media sites; safety services; and emergency assistance.

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    The best part of Penn State is our people. Our students, faculty, staff, alumni, and friends in communities near our campuses and across the globe are dedicated to education and fostering a diverse and inclusive environment.

  • richardmitnick 8:37 pm on January 27, 2020 Permalink | Reply
    Tags: "How to take a picture of a light pulse", , Laser Technology, , ,   

    From Techniche Universität Wein (Vienna) via phys.org: “How to take a picture of a light pulse” 

    Techniche Universitat Wein (Vienna)

    From Techniche Universität Wein (Vienna)



    Two laser pulses hitting a silicon dioxide crystal. Credit: Vienna University of Technology, TU Vienna.

    Until now, complex experimental equipment was required to measure the shape of a light pulse. A team from TU Wien (Vienna), MPI Garching and LMU Munich has now made this much easier.

    Today, modern lasers can generate extremely short light pulses, which can be used for a wide range of applications from investigating materials to medical diagnostics. For this purpose, it is important to measure the shape of the laser light wave with high accuracy. Until now, this has required a large, complex experimental setup. Now this can be done with a tiny crystal with a diameter of less than one millimeter. The new method has been developed by the MPI for Quantum Optics in Garching, the LMU Munich and the TU Wien (Vienna). The advance will now help to clarify important details about the interaction of light and matter.

    Looking at Light with Electrons

    Extremely short light pulses with a duration in the order of femtoseconds (10-15 seconds) were investigated. “In order to create an image of such light waves, they must be made to interact with electrons,” says Prof. Joachim Burgdörfer from the Institute of Theoretical Physics at the TU Wien. “The reaction of the electrons to the electric field of the laser gives us very precise information about the shape of the light pulse.”

    Previously, the common way to measure an infrared laser pulse was adding a much shorter laser pulse with a wavelength in the X-ray range. Both pulses are sent through a gas. The X-ray pulse ionizes individual atoms, electrons are released, which are then accelerated by the electric field of the infrared laser pulse. The motion of the electrons is recorded, and if the experiment is carried out many times with different time shifts between the two pulses, the shape of the infrared laser pulse can eventually be reconstructed. “The experimental effort required for this method is very high,” says Prof. Christoph Lemell (TU Vienna). “A complicated experimental setup is needed, with vacuum systems, many optical elements and detectors.”

    Measurement in Tiny Silicon Oxide Crystals

    To bypass such complications, the idea was born to measure light pulses not in a gas but in a solid: “In a gas you have to ionize atoms first to get free electrons. In a solid it is sufficient to give the electrons enough energy so that they can move through the solid, driven by the laser field,” says Isabella Floss (TU Vienna). This generates an electric current which can be directly measured.

    Tiny crystals of silicon oxide with a diameter of a few hundred micrometers are used for this purpose. They are hit by two different laser pulses: The pulse which is to be investigated can have any wavelength ranging from ultraviolet light and visible colors to long-wave infrared. While this laser pulse penetrates the crystal, another infrared pulse is fired at the target. “This second pulse is so strong that non-linear effects in the material can change the energy state of the electrons so that they become mobile. This happens at a very specific point in time, which can be tuned and controlled very precisely,” explains Joachim Burgdörfer.

    As soon as the electrons can move through the crystal, they are accelerated by the electric field of the first beam. This produces an electric current which is measured directly at the crystal. This signal contains precise information about the shape of the light pulse.

    Many Possible Applications

    At TU Wien, the effect was studied theoretically and analyzed in computer simulations. The experiment was performed at the Max Planck Institute for Quantum Optics in Garching. “Thanks to the close cooperation between theory and experiment, we have been able to show that the new method works very well, over a large frequency range, from ultraviolet to infrared,” says Christoph Lemell. “The waveform of light pulses can now be measured much more easily than before, with the help of such a much simpler and more compact setup.”

    The new method opens up many interesting applications: It should be possible to precisely characterize novel materials, to answer fundamental physical questions about the interaction of light and matter, and even to analyze complex molecules—for example, to reliably and quickly detect diseases by examining tiny blood samples.

    Science paper:
    Shawn Sederberg et al. Attosecond optoelectronic field measurement in solids.
    Nature Communications

    See the full article here .


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    Techniche Universitat Wein (Vienna) campus

    Our mission is “technology for people”. Through our research we “develop scientific excellence”,
    through our teaching we “enhance comprehensive competence”.

    TU Wien (TUW) is located in the heart of Europe, in a cosmopolitan city of great cultural diversity. For nearly 200 years, TU Wien has been a place of research, teaching and learning in the service of progress. TU Wien is among the most successful technical universities in Europe and is Austria’s largest scientific-technical research and educational institution.

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