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  • richardmitnick 8:36 pm on July 14, 2017 Permalink | Reply
    Tags: A high Mach number shock wave, High-energy plasma, Laser Technology, , , The first high-energy shock waves in a laboratory setting, U Rochester OMEGA EP Laser System   

    From PPPL: “Scientists create first laboratory generation of high-energy shock waves that accelerate astrophysical particles” 


    PPPL

    July 14, 2017
    John Greenwald

    1
    Physicist Derek Schaeffer. (Photo by Elle Starkman/Office of Communications).

    Throughout the universe, supersonic shock waves propel cosmic rays and supernova particles to velocities near the speed of light. The most high-energy of these astrophysical shocks occur too far outside the solar system to be studied in detail and have long puzzled astrophysicists. Shocks closer to Earth can be detected by spacecraft, but they fly by too quickly to probe a wave’s formation.

    2
    No image credit or caption.

    Opening the door to new understanding

    Now a team of scientists has generated the first high-energy shock waves in a laboratory setting, opening the door to new understanding of these mysterious processes. “We have for the first time developed a platform for studying highly energetic shocks with greater flexibility and control than is possible with spacecraft,” said Derek Schaeffer, a physicist at Princeton University and the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL), and lead author of a July paper in Physical Review Letters that outlines the experiments.

    Schaeffer and colleagues conducted their research on the Omega EP laser facility at the University of Rochester Laboratory for Laser Energetics.

    3
    U Rochester OMEGA EP Laser System

    U Rochester Omega Laser

    Collaborating on the project was PPPL physicist Will Fox, who designed the experiment, and researchers from Rochester and the universities of Michigan and New Hampshire. “This lets you understand the evolution of the physical processes going on inside shock waves,” Fox said of the platform.

    To produce the wave, scientists used a laser to create a high-energy plasma — a form of matter composed of atoms and charged atomic particles — that expanded into a pre-existing magnetized plasma. The interaction created, within a few billionths of a second, a magnetized shock wave that expanded at a rate of more than 1 million miles per hour, congruent with shocks beyond the solar system. The rapid velocity represented a high “magnetosonic Mach number” and the wave was “collisionless,” emulating shocks that occur in outer space where particles are too far apart to frequently collide.

    Discovery by accident

    Discovery of this method of generating shock waves actually came about by accident. The physicists had been studying magnetic reconnection, the process in which the magnetic field lines in plasma converge, separate and energetically reconnect. To investigate the flow of plasma in the experiment, researchers installed a new diagnostic on the Rochester laser facility. To their surprise, the diagnostic revealed a sharp steepening of the density of the plasma, which signaled the formation of a high Mach number shock wave.

    To simulate the findings, the researchers ran a computer code called “PSC” on the Titan supercomputer, the most powerful U.S. computer, housed at the DOE’s Oak Ridge Leadership Computing Facility.

    ORNL Cray XK7 Titan Supercomputer

    The simulation utilized data derived from the experiments and results of the model agreed well with diagnostic images of the shock formation.

    Going forward, the laboratory platform will enable new studies of the relationship between collisionless shocks and the acceleration of astrophysical particles. The platform “complements present remote sensing and spacecraft observations,” the authors wrote, and “opens the way for controlled laboratory investigations of high-Mach number shocks.”

    Support for this research came from the DOE Office of Science, the DOE INCITE Leadership Computing program, and the National Nuclear Security Administration, a semi-autonomous agency within the DOE.

    See the full article here .

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    PPPL campus

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University. PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

     
  • richardmitnick 9:24 am on July 13, 2017 Permalink | Reply
    Tags: , extraterrestrial ice can form in just billionths of a second, Laser Technology, , , Stanford scientists discover how dense, ,   

    From Stanford: “Stanford scientists discover how dense, extraterrestrial ice can form in just billionths of a second” 

    Stanford University Name
    Stanford University

    July 12, 2017
    Adam Hadhazy

    1
    At the Linac Coherent Light Source, Stanford scientists used the world’s most powerful X-ray laser to create an extraterrestrial form of ice. (Image credit: Brad Plummer).

    Stanford researchers have for the first time captured the freezing of water, molecule-by-molecule, into a strange, dense form called ice VII (“ice seven”), found naturally in otherworldly environments, such as when icy planetary bodies collide.

    In addition to helping scientists better understand those remote worlds, the findings – published online July 11 in Physical Review Letters – could reveal how water and other substances undergo transitions from liquids to solids. Learning to manipulate those transitions might open the way someday to engineering materials with exotic new properties.

    “These experiments with water are the first of their kind, allowing us to witness a fundamental disorder-to-order transition in one of the most abundant molecules in the universe,” said study lead author Arianna Gleason, a postdoctoral fellow at Los Alamos National Laboratory and a visiting scientist in the Extreme Environments Laboratory of Stanford’s School of Earth, Energy & Environmental Sciences.

    Scientists have long studied how materials undergo phase changes between gas, liquid and solid states. Phase changes can happen rapidly, however, and on the tiny scale of mere atoms. Previous research has struggled to capture the moment-to-moment action of phase transitions, and instead worked backward from stable solids in piecing together the molecular steps taken by predecessor liquids.

    “There have been a tremendous number of studies on ice because everyone wants to understand its behavior,” said study senior author Wendy Mao, an associate professor of geological sciences and a Stanford Institute for Materials and Energy Sciences (SIMES) principal investigator. “What our new study demonstrates, and which hasn’t been done before, is the ability to see the ice structure form in real time.”

    Catching ice in the act

    Those timescales became achievable thanks to the Linac Coherent Light Source, the world’s most powerful X-ray laser located at the nearby SLAC National Accelerator Laboratory. There, the science team beamed an intense, green-colored laser at a small target containing a sample of liquid water. The laser instantly vaporized layers of diamond on one side of the target, generating a rocket-like force that compressed the water to pressures exceeding 50,000 times that of Earth’s atmosphere at sea level.

    As the water compacted, a separate beam from an instrument called the X-ray Free Electron Laser arrived in a series of bright pulses only a femtosecond, or a quadrillionth of a second, long. Akin to camera flashes, this strobing X-ray laser snapped a set of images revealing the progression of molecular changes, flip book–style, while the pressurized water crystallized into ice VII. The phase change took just 6 billionths of a second, or nanoseconds. Surprisingly, during this process, the water molecules bonded into rod shapes, and not spheres as theory predicted.

    The platform developed for this study – combining high pressure with snapshot images – could help researchers probe the myriad ways water freezes, depending on pressure and temperature. Under the conditions on our planet’s surface, water crystallizes in only one way, dubbed ice Ih (“ice one-H”) or simply “hexagonal ice,” whether in glaciers or ice cube trays in the freezer.

    Delving into extraterrestrial ice types, including ice VII, will help scientists model such remote environments as comet impacts, the internal structures of potentially life-supporting, water-filled moons like Jupiter’s Europa, and the dynamics of jumbo, rocky, oceanic exoplanets called super-Earths.

    “Any icy satellite or planetary interior is intimately connected to the object’s surface,” Gleason said. “Learning about these icy interiors will help us understand how the worlds in our solar system formed and how at least one of them, so far as we know, came to have all the necessary characteristics for life.”

    Other co-authors on the study include Cindy Bolme of Los Alamos National Laboratory; Eric Galtier, Hae Ja Lee and Eduardo Granados of the SLAC National Accelerator Laboratory; Dan Dolan, Chris Seagle and Tom Ao of Sandia National Laboratories; and Suzanne Ali, Amy Lazicki, Damian Swift and Peter Celliers of Lawrence Livermore National Laboratory.

    Funding was provided by the National Science Foundation, the Los Alamos National Laboratory, the U.S. Department of Energy Office of Science, Fusion Energy Science and the SLAC National Accelerator Laboratory.

    See the full article here .

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    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

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  • richardmitnick 7:30 pm on July 11, 2017 Permalink | Reply
    Tags: , Laser Technology, ,   

    From Northwestern: “New laser design offers more inexpensive multi-color output” 

    Northwestern U bloc
    Northwestern University

    July 11, 2017
    Kristin Samuelson

    1
    Photo courtesy of John Krzesinski, 2011, Flickr

    From checkout counters at supermarkets to light shows at concerts, lasers are everywhere, and they’re a much more efficient light source than incandescent bulbs. But they’re not cheap to produce.

    A new Northwestern University study has engineered a more cost-effective laser design that outputs multi-color lasing and offers a step forward in chip-based lasers and miniaturization. The findings could allow encrypted, encoded, redundant and faster information flow in optical fibers, as well as multi-color medical imaging of diseased tissue in real time.

    The study was published July 10 in Nature Nanotechnology.

    “In our work, we demonstrated that multi-modal lasing with control over the different colors can be achieved in a single device,” said senior author Teri W. Odom, a Charles E. and Emma H. Morrison Professor of Chemistry in the Weinberg College of Arts and Sciences at Northwestern. “Compared to traditional lasers, our work is unprecedented for its stable multi-modal nanoscale lasing and our ability to achieve detailed and fine control over the lasing beams.”

    This work offers new insights into the design and mechanism of multi-modal nanoscale lasing based on structural engineering and manipulating the optical band structures of nanoparticle superlattices. Using this technology, the researchers can control the color and intensity of the light by simply varying its cavity architecture.

    See the full article here .

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    Northwestern South Campus
    South Campus

    On May 31, 1850, nine men gathered to begin planning a university that would serve the Northwest Territory.

    Given that they had little money, no land and limited higher education experience, their vision was ambitious. But through a combination of creative financing, shrewd politicking, religious inspiration and an abundance of hard work, the founders of Northwestern University were able to make that dream a reality.

    In 1853, the founders purchased a 379-acre tract of land on the shore of Lake Michigan 12 miles north of Chicago. They established a campus and developed the land near it, naming the surrounding town Evanston in honor of one of the University’s founders, John Evans. After completing its first building in 1855, Northwestern began classes that fall with two faculty members and 10 students.
    Twenty-one presidents have presided over Northwestern in the years since. The University has grown to include 12 schools and colleges, with additional campuses in Chicago and Doha, Qatar.

    Northwestern is recognized nationally and internationally for its educational programs.

     
  • richardmitnick 12:29 pm on July 9, 2017 Permalink | Reply
    Tags: , Laser Technology, ,   

    From APS Physics: “Cooperating Lasers Make Topological Defects” 

    Physics LogoAbout Physics

    Physics Logo 2

    Physics

    July 7, 2017
    David Ehrenstein

    1
    A circle of ten interacting lasers (left) can cleanly synchronize their phases, as shown by the sharp distinctions between light and dark rings near the center. But using 20 lasers (right) leads to a 20% likelihood for topological defects, where each laser’s phase is offset from its neighbors’, leading to light and dark rings that are less sharply defined. V. Pal et al., Phys. Rev. Lett. (2017).

    If you cool molten iron slowly, the electron spins can gradually align in a single direction and produce a strong magnetic field. But rapid cooling leads to magnetic domains aligned in various directions, separated by thin boundaries called topological defects. A similar phenomenon may have occurred as the Universe rapidly cooled after the big bang. To study topological defect formation in the lab without the challenges of temperature control, Nir Davidson and colleagues at the Weizmann Institute, Israel, have now developed an experimental model involving interacting laser beams.

    Weizmann Institute Campus

    Imaging the laser intensities allows them to measure the likelihood for topological defects to form for a range of parameters such as the effective “cooling rate.”

    To create their experimental model, Davidson and colleagues placed a disk containing between 10 and 30 holes arranged in a circle inside a laser cavity. This “mask” produced a set of laser beams, each emerging from a different hole and leaking a bit into its two neighboring beams, generating interactions. These interactions caused the phase differences among the beams to change over time. The evolution was so rapid that the team simply observed the final state, by recording the resulting pattern of laser intensities.

    This state represented the combined effects of about 1000 different longitudinal modes in the cavity—essentially 1000 independent experiments running simultaneously, each with a different set of initial phase relationships among the lasers. In many cases, the beams quickly synchronized their phases, but for some initial phase relationships, the beams would get “stuck” in a state where each beam was a fixed phase away from its neighbors. The team showed that, with ten lasers, there are exactly eight of these topological defect states.

    Analysis of the laser patterns allowed the researchers to measure the likelihood of topological defect formation as they varied parameters such as the number of lasers in the ring and the power of the pump light inside the cavity. They found that, with increasing pump power, topological defects became increasingly likely. The team explains this result with simulations showing that the variations in intensity among the beams drop rapidly in time when the pump power is high, whereas low power is associated with slower intensity equilibration. They say that the slower equilibration is the equivalent of a slower cooling rate, and thus, a lower likelihood for topological defects.

    This research is published in Physical Review Letters

    See the full article here .

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    Physicists are drowning in a flood of research papers in their own fields and coping with an even larger deluge in other areas of physics. How can an active researcher stay informed about the most important developments in physics? Physics highlights a selection of papers from the Physical Review journals. In consultation with expert scientists, the editors choose these papers for their importance and/or intrinsic interest. To highlight these papers, Physics features three kinds of articles: Viewpoints are commentaries written by active researchers, who are asked to explain the results to physicists in other subfields. Focus stories are written by professional science writers in a journalistic style and are intended to be accessible to students and non-experts. Synopses are brief editor-written summaries. Physics provides a much-needed guide to the best in physics, and we welcome your comments (physics@aps.org).

     
  • richardmitnick 8:17 am on July 7, 2017 Permalink | Reply
    Tags: , , , Laser Technology, , Scientists Get First Direct Look at How Electrons ‘Dance’ with Vibrating Atoms,   

    From SLAC: “Scientists Get First Direct Look at How Electrons ‘Dance’ with Vibrating Atoms” 


    SLAC Lab

    July 6, 2017
    No writer credit

    A precise new way to study materials shows this ‘electron-phonon coupling’ can be far stronger than predicted, and could potentially play a role in unconventional superconductivity.

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    In this illustration, an infrared laser beam (orange) triggers atomic vibrations in a thin layer of iron selenide, which are then recorded by ultrafast X-ray laser pulses (white) to create an ultrafast movie. The motion of the selenium atoms (red) changes the energy of the electron orbitals of the iron atoms (blue), and the resulting electron vibrations are recorded separately with a technique called ARPES (not shown). The coupling of atomic positions and electronic energies is much stronger than previously thought and may significantly impact the material’s superconductivity. (Greg Stewart/SLAC National Accelerator Laboratory)

    Scientists at the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University have made the first direct measurements, and by far the most precise ones, of how electrons move in sync with atomic vibrations rippling through an exotic material, as if they were dancing to the same beat.

    The vibrations are called phonons, and the electron-phonon coupling the researchers measured was 10 times stronger than theory had predicted – making it strong enough to potentially play a role in unconventional superconductivity, which allows materials to conduct electricity with no loss at unexpectedly high temperatures.

    What’s more, the approach they developed gives scientists a completely new and direct way to study a wide range of “emergent” materials whose surprising properties emerge from the collective behavior of fundamental particles, such as electrons. The new approach investigates these materials through experiments alone, rather than relying on assumptions based on theory.

    The experiments were carried out with SLAC’s Linac Coherent Light Source (LCLS) X-ray free-electron laser and with a technique called angle-resolved photoemission spectroscopy (ARPES) on the Stanford campus. The researchers described the study today in Science.

    SLAC/LCLS

    See the full article here .

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    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
    i1

     
  • richardmitnick 4:13 pm on July 5, 2017 Permalink | Reply
    Tags: An attosecond is to a second what a second is to 32 billion years: this is how fast the short pulses of light operated by a Free Electron Laser (FEL) particle accelerator could be operating at in the , Free Electron Lasers, Laser Technology, , STFC CLARA: (Compact Linear Accelerator for Research and Applications   

    From STFC: “CLARA milestone beams light on next generation laser technology” 

    STFC

    5 July 2017
    No writer credit found.

    An attosecond is to a second what a second is to 32 billion years. This is how fast the short pulses of light operated by a Free Electron Laser (FEL) particle accelerator could be operating at in the not too distant future, unlocking new windows of scientific exploration.

    A brand new research facility that is currently under construction at the Science and Technology Facilities Council’s (STFC) Daresbury Laboratory in Cheshire is ready to become the world’s first facility designed to develop, test and advance new technologies for this next generation of FEL accelerator. CLARA (Compact Linear Accelerator for Research and Applications) has just successfully generated its first electrons, a significant milestone in its development, as it aims to bring the UK’s world leading expertise and experience of FELs to a whole new level.

    CLARA Image 1[Compact Linear Accelerator for Research and Applications] at STFC_s Daresbury Laboratory

    CLARA Image 2 [Compact Linear Accelerator for Research and Applications] at STFC_s Daresbury Laboratory

    A FEL is unparalleled in its capability as a light source and is poised to be responsible for significant scientific breakthroughs in areas ranging from healthcare and new materials to sustainable energy. Scientists have already demonstrated its capabilities in a number of areas, from developing materials for the aero industry, to understanding new ways of controlling mosquito-borne diseases, to name a couple. But FEL technology is still at a relatively early stage and the potential for improvements is enormous. With very few FEL research capabilities in existence, new ideas and developments are extremely difficult to model and test experimentally.

    CLARA will provide the vital stepping stone between the development and testing of multiple new FEL technologies and their implementation onto any existing or planned FEL facility, in the UK or internationally.

    Professor Jim Clarke, Head of Science Division at STFC’s Accelerator Science and Technology Centre at Daresbury, said: “The next generation of FEL light sources will be a game changer in science research, and it is vital that we have the skills and facilities in place to be able to develop and test new FEL technologies. The design and development of CLARA has been particularly complex, so the generation of first electrons is a particularly exciting milestone. The impact of this is huge and will ensure that the UK has all the vital capabilities required should it choose to develop its own future FEL facility, whilst simultaneously contributing to R&D on an international scale, such as at the European XFEL in Germany.”

    CLARA’s first electrons were generated at around 4 million electron volts (MeV) and, over the next few months will go through a steady conditioning process, eventually ramping up to 50 MeV to be ready for use by the end of the year. It will also benefit from a new electron gun source that has been tested on VELA – another particle accelerator at Daresbury dedicated for research by industry. CLARA and VELA will be linked at source so that CLARA can also help support research on VELA. Once fully constructed CLARA will extend to 90 metres and its beam will reach a staggering 250 MeV – 99.99% of the speed of light! Its flexibility and tuneability means that it will be able to test out numerous FEL technologies for use in future FEL facilities, both in the UK and internationally.

    Professor Susan Smith, Head of STFC’s Daresbury Laboratory, said: “This milestone is a fantastic achievement for all STFC’s scientists, engineers and collaborators who are working on CLARA. Reaching this milestone is confirming the UK’s ability to build, develop and demonstrate its scientific skills and techniques in X-ray Free Electron Laser technology, which brings us exciting prospects for the future of next generation light sources. This is technology that will change people’s lives for the better.”

    Read further information about STFC’s Accelerator Science and Technology Centre.

    About Free Electron Lasers

    Free Electron Lasers (FELs) are an increasingly important kind of light source. Standard lasers can be very bright sources of visible light but they soon fade away in the deep ultra-violet and x-ray regions of the spectrum. FELs represent a radical alternative to conventional lasers, being the most flexible, high power and efficient generators of tuneable coherent radiation from the infra-red to the X-ray. FELs can have the optical properties that are characteristic of conventional lasers such as high spatial coherence and a near diffraction limited radiation beam, but FELs combine a high energy electron beam and a magnet called an undulator in such a way that all of the electrons emit light of the same wavelength at the same time, producing huge bursts of light. The latest FELs produce pulses of X-ray light that are powerful and fast enough for scientists to take stop-motion pictures of atoms and molecules in motion.

    See the full article here .

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    STFC Hartree Centre

    Helping build a globally competitive, knowledge-based UK economy

    We are a world-leading multi-disciplinary science organisation, and our goal is to deliver economic, societal, scientific and international benefits to the UK and its people – and more broadly to the world. Our strength comes from our distinct but interrelated functions:

    Universities: we support university-based research, innovation and skills development in astronomy, particle physics, nuclear physics, and space science
    Scientific Facilities: we provide access to world-leading, large-scale facilities across a range of physical and life sciences, enabling research, innovation and skills training in these areas
    National Campuses: we work with partners to build National Science and Innovation Campuses based around our National Laboratories to promote academic and industrial collaboration and translation of our research to market through direct interaction with industry
    Inspiring and Involving: we help ensure a future pipeline of skilled and enthusiastic young people by using the excitement of our sciences to encourage wider take-up of STEM subjects in school and future life (science, technology, engineering and mathematics)

    We support an academic community of around 1,700 in particle physics, nuclear physics, and astronomy including space science, who work at more than 50 universities and research institutes in the UK, Europe, Japan and the United States, including a rolling cohort of more than 900 PhD students.

    STFC-funded universities produce physics postgraduates with outstanding high-end scientific, analytic and technical skills who on graduation enjoy almost full employment. Roughly half of our PhD students continue in research, sustaining national capability and creating the bedrock of the UK’s scientific excellence. The remainder – much valued for their numerical, problem solving and project management skills – choose equally important industrial, commercial or government careers.

    Our large-scale scientific facilities in the UK and Europe are used by more than 3,500 users each year, carrying out more than 2,000 experiments and generating around 900 publications. The facilities provide a range of research techniques using neutrons, muons, lasers and x-rays, and high performance computing and complex analysis of large data sets.

    They are used by scientists across a huge variety of science disciplines ranging from the physical and heritage sciences to medicine, biosciences, the environment, energy, and more. These facilities provide a massive productivity boost for UK science, as well as unique capabilities for UK industry.

    Our two Campuses are based around our Rutherford Appleton Laboratory at Harwell in Oxfordshire, and our Daresbury Laboratory in Cheshire – each of which offers a different cluster of technological expertise that underpins and ties together diverse research fields.

    The combination of access to world-class research facilities and scientists, office and laboratory space, business support, and an environment which encourages innovation has proven a compelling combination, attracting start-ups, SMEs and large blue chips such as IBM and Unilever.

    We think our science is awesome – and we know students, teachers and parents think so too. That’s why we run an extensive Public Engagement and science communication programme, ranging from loans to schools of Moon Rocks, funding support for academics to inspire more young people, embedding public engagement in our funded grant programme, and running a series of lectures, travelling exhibitions and visits to our sites across the year.

    Ninety per cent of physics undergraduates say that they were attracted to the course by our sciences, and applications for physics courses are up – despite an overall decline in university enrolment.

     
  • richardmitnick 1:19 pm on July 1, 2017 Permalink | Reply
    Tags: Boulder, JILA, Laser Technology, , PTB,   

    From PTB: “The sharpest laser in the world” 

    PTB – The National Metrology Institute of Germany

    29.06.2017

    Erika Schow
    +49 531 592-9314
    erika.schow@ptb.de

    Imke Frischmuth
    +49 531 592-9323imke.frischmuth@ptb.de
    Secretariat
    Karin Conring
    Tel+49 531 592-3006
    Fax: +49 531 592-3008
    karin.conring@ptb.de

    Address
    Physikalisch-Technische Bundesanstalt
    Bundesallee 100
    38116 Braunschweig

    Contact
    Dr. Thomas Legero,
    PTB Department 4.3,
    Quantum Optics and Unit of Length
    +49 (0)531 592-4306,
    thomas.legero@ptb.de

    The Physikalisch-Technische Bundesanstalt has developed a laser with a linewidth of only 10 mHz.

    1
    One of the two silicon resonators (photo: PTB)

    No one had ever come so close to the ideal laser before: theoretically, laser light has only one single color (also frequency or wavelength). In reality, however, there is always a certain linewidth. With a linewidth of only 10 mHz, the laser that researchers from the Physikalisch-Technische Bundesanstalt (PTB) have now developed together with US researchers from JILA, a joint institute of the National Institute of Standards and Technology (NIST) and the University of Colorado, Boulder, has established a new world record. This precision is useful for various applications such as optical atomic clocks, precision spectroscopy, radioastronomy and for testing the theory of relativity. The results have been published in the current issue of Physical Review Letters.

    Lasers were once deemed a solution without problems – but that is now history. More than 50 years have passed since the first technical realization of the laser, and we cannot imagine how we could live without them today. Laser light is used in numerous applications in industry, medicine and information technologies. Lasers have brought about a real revolution in many fields of research and in metrology – or even made some new fields possible in the first place.

    One of a laser’s outstanding properties is the excellent coherence of the emitted light. For researchers, this is a measure for the light wave’s regular frequency and linewidth. Ideally, laser light has only one fixed wavelength (or frequency). In practice, the spectrum of most types of lasers can, however, reach from a few kHz to a few MHz in width, which is not good enough for numerous experiments requiring high precision.

    Research has therefore focused on developing ever better lasers with greater frequency stability and a narrower linewidth. Within the scope of a nearly 10-year-long joint project with the US colleagues from JILA in Boulder, Colorado, a laser has now been developed at PTB whose linewidth is only 10 mHz (0.01 Hz), hereby establishing a new world record. “The smaller the linewidth of the laser, the more accurate the measurement of the atom’s frequency in an optical clock. This new laser will enable us to decisively improve the quality of our clocks”, PTB physicist Thomas Legero explains.

    In addition to the new laser’s extremely small linewidth, Legero and his colleagues found out by means of measurements that the emitted laser light’s frequency was more precise than what had ever been achieved before. Although the light wave oscillates approx. 200 trillion times per second, it only gets out of sync after 11 seconds. By then, the perfect wave train emitted has already attained a length of approx. 3.3 million kilometers. This length corresponds to nearly ten times the distance between the Earth and the moon.

    Since there was no other comparably precise laser in the world, the scientists working on this collaboration had to set up two such laser systems straight off. Only by comparing these two lasers was it possible to prove the outstanding properties of the emitted light.

    The core piece of each of the lasers is a 21-cm long Fabry-Pérot silicon resonator. The resonator consists of two highly reflecting mirrors which are located opposite each other and are kept at a fixed distance by means of a double cone. Similar to an organ pipe, the resonator length determines the frequency of the wave which begins to oscillate, i.e., the light wave inside the resonator. Special stabilization electronics ensure that the light frequency of the laser constantly follows the natural frequency of the resonator. The laser’s frequency stability – and thus its linewidth – then depends only on the length stability of the Fabry-Pérot resonator.

    The scientists at PTB had to isolate the resonator nearly perfectly from all environmental influences which might change its length. Among these influences are temperature and pressure variations, but also external mechanical perturbations due to seismic waves or sound. They have attained such perfection in doing so that the only influence left was the thermal motion of the atoms in the resonator. This “thermal noise” corresponds to the Brownian motion in all materials at a finite temperature, and it represents a fundamental limit to the length stability of a solid. Its extent depends on the materials used to build the resonator as well as on the resonator’s temperature.

    For this reason, the scientists of this collaboration manufactured the resonator from single-crystal silicon which was cooled down to a temperature of -150 °C. The thermal noise of the silicon body is so low that the length fluctuations observed only originate from the thermal noise of the dielectric SiO2/Ta2O5 mirror layers. Although the mirror layers are only a few micrometers thick, they dominate the resonator’s length stability. In total, the resonator length, however, only fluctuates in the range of 10 attometers. This length corresponds to no more than a ten-millionth of the diameter of a hydrogen atom. The resulting frequency variations of the laser therefore amount to less than 4 × 10–17 of the laser frequency.

    The new lasers are now being used both at PTB and at JILA in Boulder to further improve the quality of optical atomic clocks and to carry out new precision measurements on ultracold atoms. At PTB, the ultrastable light from these lasers is already being distributed via optical waveguides and is then used by the optical clocks in Braunschweig.

    “In the future, it is planned to disseminate this light also within a European network. This plan would allow even more precise comparisons between the optical clocks in Braunschweig and the clocks of our European colleagues in Paris and London”, Legero says. In Boulder, a similar plan is in place to distribute the laser across a fiber network that connects between JILA and various NIST labs.

    The scientists from this collaboration see further optimization possibilities. With novel crystalline mirror layers and lower temperatures, the disturbing thermal noise can be further reduced. The linewidth could then even become smaller than 1 mHz.

    See the full article here .

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    The Physikalisch-Technische Bundesanstalt, the National Metrology Institute of Germany, is a scientific and technical higher federal authority falling within the competence of the Federal Ministry for Economic Affairs and Energy.

    PTB is Germany’s highest authority when it comes to correct and reliable measurements. It is the supreme technical authority of the Federal Ministry for Economic Affairs and Energy (BMWi) and employs a total of approx. 1900 staff members. PTB operates an integrated Opens internal link in current windowquality management system which covers the four interlinked field of business.

     
  • richardmitnick 12:22 pm on June 27, 2017 Permalink | Reply
    Tags: 1 billion suns: World’s brightest laser sparks new behavior in light, Diocles Laser, Extreme Light Laboratory, Focusing laser light to a brightness 1 billion times greater than the surface of the sun, Laser Technology, , , U Nebraska,   

    From U Nebraska – Lincoln: “1 billion suns: World’s brightest laser sparks new behavior in light” 

    University of Nebraska -Lincoln

    6.26.17
    Scott Schrage

    1
    A rendering of how changes in an electron’s motion (bottom) alter the scattering of light (top), as measured in a new experiment that scattered more than 500 photons of light from a single electron. Previous experiments had managed to scatter no more than a few photons at a time. Donald Umstadter and Wenchao Yan

    4
    Brighter than a billion suns: A scientist at work in the Extreme Light Laboratory. Diocles Laser.
    University of Nebraska-Lincoln. COSMOS.

    Physicists from the University of Nebraska-Lincoln are seeing an everyday phenomenon in a new light.

    By focusing laser light to a brightness 1 billion times greater than the surface of the sun — the brightest light ever produced on Earth — the physicists have observed changes in a vision-enabling interaction between light and matter.

    Those changes yielded unique X-ray pulses with the potential to generate extremely high-resolution imagery useful for medical, engineering, scientific and security purposes. The team’s findings, detailed June 26 in the journal Nature Photonics, should also help inform future experiments involving high-intensity lasers.

    Donald Umstadter and colleagues at the university’s Extreme Light Laboratory fired their Diocles Laser at helium-suspended electrons to measure how the laser’s photons — considered both particles and waves of light — scattered from a single electron after striking it.

    Under typical conditions, as when light from a bulb or the sun strikes a surface, that scattering phenomenon makes vision possible. But an electron — the negatively charged particle present in matter-forming atoms — normally scatters just one photon of light at a time. And the average electron rarely enjoys even that privilege, Umstadter said, getting struck only once every four months or so.

    Though previous laser-based experiments had scattered a few photons from the same electron, Umstadter’s team managed to scatter nearly 1,000 photons at a time. At the ultra-high intensities produced by the laser, both the photons and electron behaved much differently than usual.

    “When we have this unimaginably bright light, it turns out that the scattering — this fundamental thing that makes everything visible — fundamentally changes in nature,” said Umstadter, the Leland and Dorothy Olson Professor of Physics and Astronomy.

    A photon from standard light will typically scatter at the same angle and energy it featured before striking the electron, regardless of how bright its light might be. Yet Umstadter’s team found that, above a certain threshold, the laser’s brightness altered the angle, shape and wavelength of that scattered light.

    “So it’s as if things appear differently as you turn up the brightness of the light, which is not something you normally would experience,” Umstadter said. “(An object) normally becomes brighter, but otherwise, it looks just like it did with a lower light level. But here, the light is changing (the object’s) appearance. The light’s coming off at different angles, with different colors, depending on how bright it is.”

    That phenomenon stemmed partly from a change in the electron, which abandoned its usual up-and-down motion in favor of a figure-8 flight pattern. As it would under normal conditions, the electron also ejected its own photon, which was jarred loose by the energy of the incoming photons. But the researchers found that the ejected photon absorbed the collective energy of all the scattered photons, granting it the energy and wavelength of an X-ray.

    The unique properties of that X-ray might be applied in multiple ways, Umstadter said. Its extreme but narrow range of energy, combined with its extraordinarily short duration, could help generate three-dimensional images on the nanoscopic scale while reducing the dose necessary to produce them.

    3
    Using a laser focused to the brightest intensity yet recorded, physicists at the Extreme Light Laboratory produced unique X-ray pulses with greater energy than their conventional counterparts. The team demonstrated these X-rays by imaging the circuitry of a USB drive. Extreme Light Laboratory | University of Nebraska-Lincoln.

    Those qualities might qualify it to hunt for tumors or microfractures that elude conventional X-rays, map the molecular landscapes of nanoscopic materials now finding their way into semiconductor technology, or detect increasingly sophisticated threats at security checkpoints. Atomic and molecular physicists could also employ the X-ray as a form of ultrafast camera to capture snapshots of electron motion or chemical reactions.

    As physicists themselves, Umstadter and his colleagues also expressed excitement for the scientific implications of their experiment. By establishing a relationship between the laser’s brightness and the properties of its scattered light, the team confirmed a recently proposed method for measuring a laser’s peak intensity. The study also supported several longstanding hypotheses that technological limitations had kept physicists from directly testing.

    “There were many theories, for many years, that had never been tested in the lab, because we never had a bright-enough light source to actually do the experiment,” Umstadter said. “There were various predictions for what would happen, and we have confirmed some of those predictions.

    “It’s all part of what we call electrodynamics. There are textbooks on classical electrodynamics that all physicists learn. So this, in a sense, was really a textbook experiment.”

    Umstadter authored the study with Sudeep Banerjee and Shouyuan Chen, research associate professors of physics and astronomy; Grigory Golovin and Cheng Liu, senior research associates in physics and astronomy; Wenchao Yan, Ping Zhang, Baozhen Zhao and Jun Zhang, postdoctoral researchers in physics and astronomy; Colton Fruhling and Daniel Haden, doctoral students in physics and astronomy; along with Min Chen and Ji Luo of Shanghai Jiao Tong University.

    The team received support from the Air Force Office for Scientific Research, the National Science Foundation, the U.S. Department of Energy’s Office of Science, the Department of Homeland Security’s Domestic Nuclear Detection Office, and the National Science Foundation of China.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

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    The University of Nebraska–Lincoln, often referred to as Nebraska, UNL or NU, is a public research university in the city of Lincoln, in the state of Nebraska in the Midwestern United States. It is the state’s oldest university, and the largest in the University of Nebraska system.

    The state legislature chartered the university in 1869 as a land-grant university under the 1862 Morrill Act, two years after Nebraska’s statehood into the United States. Around the turn of the 20th century, the university began to expand significantly, hiring professors from eastern schools to teach in the newly organized professional colleges while also producing groundbreaking research in agricultural sciences. The “Nebraska method” of ecological study developed here during this time pioneered grassland ecology and laid the foundation for research in theoretical ecology for the rest of the 20th century. The university is organized into eight colleges on two campuses in Lincoln with over 100 classroom buildings and research facilities.

    Its athletic program, called the Cornhuskers, is a member of the Big Ten Conference. The Nebraska football team has won 46 conference championships, and since 1970, five national championships. The women’s volleyball team has won four national championships along with eight other appearances in the Final Four. The Husker football team plays its home games at Memorial Stadium, selling out every game since 1962. The stadium’s capacity is about 92,000 people, larger than the population of Nebraska’s third-largest city.

     
  • richardmitnick 8:06 am on June 23, 2017 Permalink | Reply
    Tags: A Single Electron’s Tiny Leap Sets Off ‘Molecular Sunscreen’ Response, , , , Laser Technology, , ,   

    From SLAC: “A Single Electron’s Tiny Leap Sets Off ‘Molecular Sunscreen’ Response” 


    SLAC Lab

    June 22, 2017
    Glennda Chui

    1
    Thymine – the molecule illustrated in the foreground – is one of the four basic building blocks that make up the double helix of DNA. It’s such a strong absorber of ultraviolet light that the UV in sunlight should deactivate it, yet this does not happen. Researchers used an X-ray laser at SLAC National Accelerator Laboratory to observe the infinitesimal leap of a single electron that sets off a protective response in thymine molecules, allowing them to shake off UV damage. (Greg Stewart/SLAC National Accelerator Laboratory)

    In experiments at the Department of Energy’s SLAC National Accelerator Laboratory, scientists were able to see the first step of a process that protects a DNA building block called thymine from sun damage: When it’s hit with ultraviolet light, a single electron jumps into a slightly higher orbit around the nucleus of a single oxygen atom.

    This infinitesimal leap sets off a response that stretches one of thymine’s chemical bonds and snaps it back into place, creating vibrations that harmlessly dissipate the energy of incoming ultraviolet light so it doesn’t cause mutations.

    The technique used to observe this tiny switch-flip at SLAC’s Linac Coherent Light Source (LCLS) X-ray free-electron laser can be applied to almost any organic molecule that responds to light – whether that light is a good thing, as in photosynthesis or human vision, or a bad thing, as in skin cancer, the scientists said. They described the study in Nature Communications today.

    SLAC/LCLS

    “All of these light-sensitive organic molecules tend to absorb light in the ultraviolet. That’s not only why you get sunburn, but it’s also why your plastic eyeglass lenses offer some UV protection,” said Phil Bucksbaum, a professor at SLAC and Stanford University and director of the Stanford PULSE Institute at SLAC. “You can even see these effects in plastic lawn furniture – after a couple of seasons it can become brittle and discolored simply due to the fact that the plastic was absorbing ultraviolet light all the time, and the way it absorbs sun results in damage to its chemical bonds.”

    Catching Electrons in Action

    Thymine and the other three DNA building blocks also strongly absorb ultraviolet light, which can trigger mutations and skin cancer, yet these molecules seem to get by with minimal damage. In 2014, a team led by Markus Guehr ­– then a SLAC senior staff scientist and now on the faculty of the University of Potsdam in Germany – reported that they had found the answer: The stretch-snap of a single bond and resulting energy-dissipating vibrations, which took place within 200 femtoseconds, or millionths of a billionth of a second after UV light exposure.

    But what made the bond stretch? The team knew the answer had to involve electrons, which are responsible for forming, changing and breaking bonds between atoms. So they devised an ingenious way to catch the specific electron movements that trigger the protective response.

    It relied on the fact that electrons don’t orbit an atom’s nucleus in neat concentric circles, like planets orbiting a sun, but rather in fuzzy clouds that take a different shape depending on how far they are from the nucleus. Some of these orbitals are in fact like a fuzzy sphere; others look a little like barbells or the start of a balloon animal. You can see examples here.

    2
    No image caption or credit, but there is a comment,
    “I see the distribution in different orbitals. So if for example I take the S orbitals, they are all just a sphere. So wont the 2S orbital overlap with the 1S overlap, making the electrons in each orbital “meet” at some point? Or have I misunderstood something?”

    Strong Signal Could Solve Long-Standing Debate

    For this new experiment, the scientists hit thymine molecules with a pulse of UV laser light and tuned the energy of the LCLS X-ray laser pulses so they would home in on the response of the oxygen atom that’s at one end of the stretching, snapping bond.

    The energy from the UV light excited one of the atom’s electrons to jump into a higher orbital. This left the atom in a sort of tippy state where just a little more energy would boost a second electron into a higher orbital; and that second jump is what sets off the protective response, changing the shape of the molecule just enough to stretch the bond.

    The first jump, which was previously known to happen, is difficult to detect because the electron winds up in a rather diffuse orbital cloud, Guehr said. But the second, which had never been observed before, was much easier to spot because that electron ended up in an orbital with a distinctive shape that gave off a big signal.

    “Although this was a very tiny electron movement, the signal kind of jumped out at us in the experiment,” Guehr said. “I always had a feeling this would be a strong transition, just intuitively, but when we saw this come in it was a special moment, one of the best moments an experimentalist can have.”

    Settling a Longstanding Debate

    Study lead author Thomas Wolf, an associate staff scientist at SLAC, said the results should settle a longstanding debate about how long after UV exposure the protective response kicks in: It happens 60 femtoseconds after UV light hits. This time span is important, he said, because the longer the atom spends in the tippy state between the first jump and the second, the more likely it is to undergo some sort of reaction that could damage the molecule.

    Henrik Koch, a theorist at NTNU in Norway who was a guest professor at Stanford at the time, led the study with Guehr. He led the effort to model, understand and interpret what happened in the experiment, and he participated in it to an unusual extent, Guehr said.

    “He is extremely experienced in applying theory to methodology development, and he had this curiosity to bring this to our experiment,” Guehr said. “He was so fascinated by this research that he did something completely untypical of a theorist – he came to LCLS, into the control room, and he wanted to see the data coming in. I found that completely amazing and very motivating. It turned out that some of my previous thinking was completely right but other aspects were completely wrong, and Henrik did the right theory at the right level so we could learn from it.”

    See the full article here .

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    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
    i1

     
  • richardmitnick 9:58 am on June 5, 2017 Permalink | Reply
    Tags: 'Scrambled light' wavemeter breakthrough, , , Laser Technology, Laser wavemeters, Quantum technologies and healthcare, U St Andrews   

    From St. Andrews: “‘Scrambled light’ wavemeter breakthrough” 

    U St Andrews bloc

    University of St Andrews

    05 June 2017
    No writer credit found

    1
    A breakthrough innovation in the measurement of lasers can measure changes one millionth of the size of an atom and could revolutionize their use in quantum technologies and healthcare thanks to new, lower-cost technology. No image credit.

    A team from the University of St Andrews and UK company M Squared Lasers has used the principle of random scattering of light to create a new class of laser wavemeter that breaks through a glass ceiling in the way wavelength is measured.

    Wavemeters are used in many areas of science to identify the wavelength (i.e. colour) of light. All atoms and molecules absorb light at very precise wavelengths, therefore the ability to identify and manipulate them at high resolution is important in diverse fields ranging from the identification of biological and chemical samples to the cooling of individual atoms to temperatures colder than the depths of outer space

    Waves, whether they are water waves or light waves, interact via interference: sometimes two waves reach a peak at the same time and place and the result is a higher wave, but it is also possible that a peak of one wave meets the trough of another, resulting in a smaller wave. The combination of these effects produces an interference pattern.

    Conventional wavemeters analyse changes in the interference pattern produced by delicate assemblies of high-precision optical components. The cheapest instruments cost hundreds or thousands of pounds, and most in everyday research use cost tens of thousands.

    In contrast, the team realised a robust and low-cost device which surpasses the resolution of all commercially-available wavemeters. They did this by shining laser light inside a 5 cm diameter sphere which had been painted white, and recording images of the light which escapes through a small hole. The pattern formed by the light is incredibly sensitive to the wavelength of the laser.

    Dr Graham Bruce from the School of Physical and Astronomy explains:

    “If you take a laser pointer, and shine it through Sellotape or on a rough surface like a painted wall, on closer inspection of the illuminated surface you’ll see that the spot itself looks grainy or speckled, with bright and dark patches. This so-called ‘speckle pattern’ is a result of interference between the various parts of the beam which are reflected differently by the rough surface.

    “This speckle pattern might seem of little use but in fact the pattern is rich in information about the illuminating laser.

    “The pattern produced by the laser through any such scattering medium is in fact very sensitive to a change in the laser’s parameters and this is what we’ve made use of.”

    The breakthrough, which has been published in the prestigious journal Nature Communications, opens a new route for ultra-high precision measurement of laser wavelength, realizing a precision of close to one part in three billion, which is around 10 to 100 times better than current commercial devices.

    This precision allowed the team to measure tiny changes in wavelength below 1 femtometre: equivalent to just one millionth of the diameter of a single atom.

    They also showed that this sensitive measurement could be used to actively stabilize the wavelength of the laser.

    In future, the team hope to demonstrate the use of such approaches for quantum technology applications in space and on Earth, as well as to measure light scattering for biomedical studies in a new, inexpensive way.

    Professor Kishan Dholakia from the School of Physical and Astronomy said:

    “This is an exciting team effort for what we believe is a major breakthrough in the field. It is a testament to strong UK industry–university co-operation and links to future commercial opportunities with quantum technologies and those in healthcare.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

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    U St Andrews campus

    St Andrews is made up from a variety of institutions, including three constituent colleges (United College, St Mary’s College, and St Leonard’s College) and 18 academic schools organised into four faculties. The university occupies historic and modern buildings located throughout the town. The academic year is divided into two terms, Martinmas and Candlemas. In term time, over one-third of the town’s population is either a staff member or student of the university. The student body is notably diverse: over 120 nationalities are represented with over 45% of its intake from countries outside the UK; about one-eighth of the students are from the rest of the EU and the remaining third are from overseas — 15% from North America alone. The university’s sport teams compete in BUCS competitions, and the student body is known for preserving ancient traditions such as Raisin Weekend, May Dip, and the wearing of distinctive academic dress.

     
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