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  • richardmitnick 11:52 am on March 1, 2017 Permalink | Reply
    Tags: , Laser Technology, , Scientists develop spectacles for X-ray lasers, X-ray laser beam,   

    From DESY: “Scientists develop spectacles for X-ray lasers” 

    DESY
    DESY

    2017/03/01

    Tailor-made corrective glasses permit unparalleled concentration of X-ray beam

    An international team of scientists has tailored special X-ray glasses to concentrate the beam of an X-ray laser stronger than ever before. The individually produced corrective lens eliminates the inevitable defects of an X-ray optics stack almost completely and concentrates three quarters of the X-ray beam to a spot with 250 nanometres (millionths of a millimetre) diameter, closely approaching the theoretical limit. The concentrated X-ray beam can not only improve the quality of certain measurements, but also opens up entirely new research avenues, as the team surrounding DESY lead scientist Christian Schroer writes in the journal Nature Communications.

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    Profile of the focused X-ray beam, without (top) and with (bottom) the corrective lens. Credit: Frank Seiboth, DESY

    Although X-rays obey the same optical laws as visible light, they are difficult to focus or deflect: “Only a few materials are available for making suitable X-ray lenses and mirrors,” explains co-author Andreas Schropp from DESY. “Also, since the wavelength of X-rays is very much smaller than that of visible light, manufacturing X-ray lenses of this type calls for a far higher degree of precision than is required in the realm of optical wavelengths – even the slightest defect in the shape of the lens can have a detrimental effect.”

    The production of suitable lenses and mirrors has already reached a very high level of precision, but the standard lenses, made of the element beryllium, are usually slightly too strongly curved near the centre, as Schropp notes. “Beryllium lenses are compression-moulded using precision dies. Shape errors of the order of a few hundred nanometres are practically inevitable in the process.” This results in more light scattered out of the focus than unavoidable due to the laws of physics. What’s more, this light is distributed quite evenly over a rather large area.

    2
    The X-ray spectacles under an electron microscope. Credit: DESY NanoLab

    Such defects are irrelevant in many applications. “However, if you want to heat up small samples using the X-ray laser, you want the radiation to be focussed on an area as small as possible,” says Schropp. “The same is true in certain imaging techniques, where you want to obtain an image of tiny samples with as much details as possible.”

    In order to optimise the focussing, the scientists first meticulously measured the defects in their portable beryllium X-ray lens stack. They then used these data to machine a customised corrective lens out of quartz glass, using a precision laser at the University of Jena. The scientists then tested the effect of these glasses using the LCLS X-ray laser at SLAC National Accelerator Laboratory in the U.S.

    “Without the corrective glasses, our lens focused about 75 per cent of the X-ray light onto an area with a diameter of about 1600 nanometres. That is about ten times as large as theoretically achievable,” reports principal author Frank Seiboth from the Technical University of Dresden, who now works at DESY. “When the glasses were used, 75 per cent of the X-rays could be focused into an area of about 250 nanometres in diameter, bringing it close to the theoretical optimum.” With the corrective lens, about three times as much X-ray light was focused into the central speckle than without it. In contrast, the full width at half maximum (FWHM), the generic scientific measure of focus sharpness in optics, did not change much and remained at about 150 nanometres, with or without the glasses.

    3
    Scheme of the experimental set-up. Credit: Frank Seiboth, DESY

    The same combination of mobile standard optics and tailor-made glasses has also been studied by the team at DESY’s synchrotron X-ray source PETRA III and the British Diamond Light Source. In both cases, the corrective lens led to a comparable improvement to that seen at the X-ray laser. “In principle, our method allows an individual corrective lens to be made for every X-ray optics,” explains lead scientist Schroer, who is also a professor of physics at the University of Hamburg.

    “These so-called phase plates can not only benefit existing X-ray sources, but in particular they could become a key component of next-generation X-ray lasers and synchrotron light sources,” emphasises Schroer. “Focusing X-rays to the theoretical limits is not only a prerequisite for a substantial improvement in a range of different experimental techniques; it can also pave the way for completely new methods of investigation. Examples include the non-linear scattering of particles of light by particles of matter, or creating particles of matter from the interaction of two particles of light. For these methods, the X-rays need to be concentrated in a tiny space which means efficient focusing is essential.”

    Involved in this research project were the Technical University of Dresden, the Universities of Jena and Hamburg, KTH Royal Institute of Technology in Stockholm, Diamond Light Source, SLAC National Accelerator Laboratory and DESY.

    See the full article here .

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    DESY is one of the world’s leading accelerator centres. Researchers use the large-scale facilities at DESY to explore the microcosm in all its variety – from the interactions of tiny elementary particles and the behaviour of new types of nanomaterials to biomolecular processes that are essential to life. The accelerators and detectors that DESY develops and builds are unique research tools. The facilities generate the world’s most intense X-ray light, accelerate particles to record energies and open completely new windows onto the universe. 
That makes DESY not only a magnet for more than 3000 guest researchers from over 40 countries every year, but also a coveted partner for national and international cooperations. Committed young researchers find an exciting interdisciplinary setting at DESY. The research centre offers specialized training for a large number of professions. DESY cooperates with industry and business to promote new technologies that will benefit society and encourage innovations. This also benefits the metropolitan regions of the two DESY locations, Hamburg and Zeuthen near Berlin.

     
  • richardmitnick 3:29 pm on February 2, 2017 Permalink | Reply
    Tags: , Department of Energy fusion laser research and development, Diode-pumped petawatt lasers, ELI Beamlines - European Extreme Light Infrastructure Beamlines, High-Repetition-Rate Advanced Petawatt Laser System (HAPLS), Laser Technology,   

    From LLNL: “LLNL meets key milestone for delivery of world’s highest average power petawatt laser system” This is a Big Deal 


    Lawrence Livermore National Laboratory

    Feb. 2, 2017

    Breanna Bishop
    bishop33@llnl.gov
    925-423-9802

    [THIS IS A BIG DEAL, US DEVELOPED TECHNOLOGY FOR EXPORT.]

    1
    HAPLS has set a world record for diode-pumped petawatt lasers, with energy reaching 16 joules and a 28 femtosecond pulse duration (equivalent to ~0.5 petawatt/pulse) at a 3.3 hertz repetition rate (3.3 times per second).

    The High-Repetition-Rate Advanced Petawatt Laser System (HAPLS), being developed at Lawrence Livermore National Laboratory (LLNL), recently completed a significant milestone: demonstration of continuous operation of an all diode-pumped, high-energy femtosecond petawatt laser system.

    With completion of this milestone, the system is ready for delivery and integration at the European Extreme Light Infrastructure Beamlines facility project (ELI Beamlines) in the Czech Republic.

    2
    e
    ELI Beamlines

    HAPLS set a world record for diode-pumped petawatt lasers, with energy reaching 16 joules (J) and a 28 femtosecond (fs) pulse duration (equivalent to ~0.5 petawatt/pulse) at a 3.3 hertz (Hz) repetition rate (3.3 times per second).

    In just three years, HAPLS went from concept to a fully integrated and record-breaking product. HAPLS represents a new generation of application-enabling diode-pumped, high-energy and high-peak-power laser systems with innovative technologies originating from the Department of Energy fusion laser research and development.

    “Lawrence Livermore takes pride in pushing science and technology to regimes never achieved before,” LLNL Director Bill Goldstein said. “Twenty years ago, LLNL pioneered the first petawatt laser, the NOVA Petawatt, representing a quantum leap forward in peak power. Today, HAPLS leads a new generation of petawatt lasers, with capabilities not seen before.”

    6
    The Nova laser at Lawrence Livermore National Laboratory in California, completed in 1984, was the world’s largest working laser until its retirement in 1999. With 10 laser beams, it was used for experiments on x-rays, astronomical phenomena, and fusion energy. In 1996, it was made into a petawatt laser, in which a short, intense pulse produced the highest power yet achieved: about 1.3 petawatts, or 1.3 quadrillion watts.

    In the decades since high-power lasers were introduced, they have illuminated entirely new fields of scientific endeavor, in addition to making profound impacts on society. When petawatt peak power pulses are focused to a high intensity on a target, they generate secondary sources such as electromagnetic radiation (for example, high-brightness X-rays) or accelerate charged particles (electrons, protons or ions), enabling unparalleled access to a variety of research areas, including time-resolved proton and X-ray radiography, laboratory astrophysics and other basic science and medical applications for cancer treatments, in addition to national security applications and industrial processes such as nondestructive evaluation of materials and laser fusion.

    Up to now, proof-of-principle experiments with single-shot lasers have provided a glimpse into this arena of transformational applications, but to commercially explore these areas a high-repetition-rate petawatt laser is needed.

    “The high-repetition-rate of the HAPLS system is a watershed moment for the community,” said Constantin Haefner, LLNL’s program director for Advanced Photon Technologies (APT). “HAPLS is the first petawatt laser to truly provide application-enabling repetition rates.”

    Drawing on LLNL’s decades of cutting-edge laser research and development led to the key advancements that distinguish HAPLS from other petawatt lasers. Those advancements include HAPLS’ ability to reach petawatt power levels while maintaining an unprecedented pulse rate; development of the world’s highest peak power diode arrays…

    5
    To drive the diode arrays, LLNL needed to develop a completely new type of pulsed-power system, which supplies the arrays with electrical power by drawing energy from the grid and converting it to extremely high-current, precisely-shaped electrical pulses.Photos by Damien Jemison.

    …driven by a Livermore-developed pulsed power system; a pump laser generating up to 200 J at a 10 Hz repetition rate; a gas-cooled short-pulse titanium-doped sapphire amplifier; a sophisticated control system with a high level of automation including auto-alignment capability, fast laser startup, performance tracking and machine safety; dual chirped-pulse-amplification high-contrast short-pulse front end; and a gigashot laser pump source for pumping the short-pulse preamplifiers. In addition, HAPLS is to be the most compact petawatt laser ever built.

    This expertise is why ELI Beamlines looked to Livermore to develop HAPLS. “It was quite straightforward,” said Roman Hvezda, ELI Beamlines project manager. “Given the design requirements, nobody else could deliver this system in such a short time on schedule and on budget. It’s a great benefit to be able to cooperate with Livermore, a well-established lab, and this will be a basis for continued cooperation in the future.”

    This cooperation was daily during construction, with LLNL and ELI Beamlines scientists and engineers working side by side on all parts of the laser system.

    “One of the real successes of this endeavor was that very early on, the client was fully integrated into the commissioning and operation of this laser,” Haefner said. “This provided hands-on training and expertise right out of the gate, helping to ensure operational success once the laser is installed at ELI Beamlines. We look at this as a long-term and enduring partnership.”

    Bedrich Rus, ELI Beamlines scientific coordinator for Laser Technology, agrees. “This was never a standard client-supplier relationship,” he said. “We have had about 10 people at LLNL – this integration is not only a very positive added value for the future operation of the facility, it’s been a great experience for their careers and development.”

    In the coming months, HAPLS will be transferred to ELI Beamlines, where it will be integrated into the facility’s laser beam transport and control systems, then brought up to full design specification – delivery of pulses with peak power exceeding 1 petawatt (quadrillion watts) firing at 10 Hz, breaking its own record and making it the world’s highest average power petawatt system. ELI plans to make HAPLS available by 2018 to the international science user community to conduct the first experiments using the laser.

    “HAPLS was a very fast-paced project,” Haefner said. “In only three years it pushed the cutting edge in high-power short-pulse lasers more than tenfold, incorporating a completely new system approach. To do so, Livermore worked closely with industry to similarly advance the state of the art – and many of those joint Livermore/industry innovations are already on the market. These partnerships can be incredibly synergistic, resulting in successful and societal impactful technologies like HAPLS.”

    See the full article here .

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  • richardmitnick 10:26 am on January 26, 2017 Permalink | Reply
    Tags: , Britain's Central Laser Facility (CLF), DiPOLE 100 laser, HiLASE's plan for the laser, Laser Technology,   

    From Science Alert: “Scientists claim they’ve built the most powerful pulse laser on Earth” 

    ScienceAlert

    Science Alert

    25 JAN 2017
    BEC CREW

    1
    Georgy Shafeev/Shutterstock,com

    This we need to see.

    Scientists say they’ve successfully tested a new US$48 million ‘super laser’, and they’re claiming it’s 10 times more powerful than any other laser of its kind on the planet, with an average power output of 1,000 watts.

    If that doesn’t sound all that powerful to you, you’re right – there’s a laser in Japan that can hit peak outputs of more than 1 trillion watts. But this new pulse laser doesn’t blow everything on a single burst – it can reportedly fire high-powered beams many times over, and with more power than any other technology on the planet.

    The laser has been built by Britain’s Central Laser Facility (CLF), and HiLASE (High average power pulsed laser), a Czech state research and development project run by the country’s Institute of Physics.

    “It is a world record which is important,” director of the CLF, John Collier, told AFP.

    “It is good for putting things on the map, but the more important point is that the underlying technology that has been developed here is going to transform the application of these high power, high energy lasers.”

    Let’s get one thing straight right off the bat – a world record is a mighty big claim, and the team has yet to release a peer-reviewed paper to support it. So until the numbers are independently verified, we’ll have to take their word for it, but it’s by no means official.

    But the Czech researchers have had a plan in place to hit this specific record since 2011, and Central Laser Facility has been developing laser technology for over four decades now, and currently have five active laser labs in operation, so these are not new players in the laser game.

    The team claims to have achieved the record last month at a testing facility in Dolní Břežany – a municipality near Prague in the Czech Republic.

    Their DiPOLE 100 laser (nicknamed Bivoj, after a Hercules-like hero in Czech mythology), reportedly hit an average of 1,000 watts for over 1 hour without intervention, and the team asserts that this kind of sustained, high-energy pulsing is unrivalled.

    When we talk about the world’s most powerful lasers, there are two very different types – there are continuous lasers, which fire constant beams of energy, and there are pulse lasers, which can fire in short, powerful bursts.

    The DiPOLE 100 is a pulse laser, and the two other largest high-power pulse lasers in existence are the Texas Petawatt Laser in Austin, and the 2-petawatt Laser for Fast Ignition Experiments (LFEX) in Osaka, Japan.

    Those lasers “have a very high peak power, but they can only reach it several times a day,” HiLASE director Tomas Mocek told AFP.

    “They do not have so-called average power. This is a combination of the repetition rate and the energy. Our laser has the highest average power, which is important. The repetition rate in Osaka and Austin is significantly lower.”

    What’s really cool about this announcement – if it can be confirmed in a published paper – is that it adds a new kind of diversity to the world’s best high-powered pulse lasers, and could be really useful for researchers of the future.

    So while the Texas Petawatt Laser could be used to run a couple of experiments per day, helping researchers peer into exotic states of matter and ultra-high electromagnetic fields, the DiPOLE 100 provides a constant stream of highly focussed laser energy for things like particle acceleration and X-ray generation.

    The team plans on commercialising it by the end of 2017, so let’s hope some great science comes of it.

    For more information on the project, you can check out HiLASE’s plan for the laser.

    See the full article here .

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  • richardmitnick 3:35 pm on December 6, 2016 Permalink | Reply
    Tags: , Laser Technology,   

    From Technion via Futurism: “Scientists Have Created a Totally New Type of Laser With Light and Water Waves” 

    Technion bloc

    Technion

    1

    Futurism

    12.6.16
    Dom Galeon

    In Brief

    Using a device smaller than the width of a human hair, scientists have produced laser radiation through the interaction of light and water waves, a first in the field of laser tech.
    This new type of laser could be used on tiny ‘lab-on-a-chip’ technologies, enabling researchers to more effectively study microscopic cells and test different drug therapies.

    Of Waves and Lightwaves

    There’s a new kid in town with respect to laser technology. Researchers at the Technion–Israel Institute of Technology have developed laser emissions through the interaction of light and water waves, combining two areas of study previously thought unrelated.

    Typically, lasers are produced by exciting electrons in atoms using energy from an outside source. This excitement causes the electrons to emit radiation as laser light. The Technion team, led by Tal Carmon, discovered that wave oscillations in a liquid device can produce laser radiation as well, according to the study published in Nature Photonics.

    This possibility had never been explored previously, Carmon told Phys.org, primarily due to enormous differences in frequencies between water waves on a liquid’s surface and light wave oscillations. The former have a low frequency of approximately 1,000 oscillations per second, while the latter have a higher frequency of around 1014 oscillations per second.

    The researchers built a device that used an optical fiber to deliver light into a small droplet of octane and water. It compensated for the otherwise low efficiency between light waves and water waves, allowing the two types to pass through each other approximately 1 million times within the droplet. The energy generated by this interaction leaves the droplet as the laser emission.

    2
    Credits: The Technion-Israel Institute of Technology

    Greater Control

    This interaction between light and fluid happens on a scale smaller than the width of a human hair. Additionally, water is a million times softer than typical materials used in existing laser technology. Accordingly, the Technion researchers say the droplet deformation caused by this very small pressure from the the light is a million times greater than what’s seen in current optomechanical devices, so this laser tech would be easier to control.

    Because they would work on such a small scale and be easier to control, this new type of laser could open up a wealth of possibilities for tiny sensors that use a combination of light waves, water waves, and sound waves. They could be used on tiny ‘lab-on-a-chip’ technologies, enabling researchers to more effectively study microscopic cells and test different drug therapies that could lead to better healthcare down the road. Indeed, these tiny lasers could have big implications in the world of technology.

    See the full article here .

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    A science and technology research university, among the world’s top ten,
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    for the advancement of the State of Israel and all humanity.

     
  • richardmitnick 8:34 am on September 30, 2016 Permalink | Reply
    Tags: , Laser Technology, , Physicists have figured out how to create matter and antimatter using light,   

    From Science Alert: “Physicists have figured out how to create matter and antimatter using light” 

    ScienceAlert

    Science Alert

    1
    Wikimedia Commons

    29 SEP 2016
    JUNE JAVELOSA, FUTURISM

    A team of researchers from the Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS) has just announced that they managed to calculate how to create matter and antimatter using lasers.

    This means that, by focusing high-powered laser pulses, we might soon be able to create matter and antimatter using light.

    To break this down a bit, light is made of high-energy photons. When high-energy photons go through strong electric fields, they lose enough radiation that they become gamma rays and create electron-positron pairs, thus creating a new state of matter.

    “A strong electric field can, generally speaking, ‘boil the vacuum,’ which is full of ‘virtual particles,’ such as electron-positron pairs. The field can convert these types of particles from a virtual state, in which the particles aren’t directly observable, to a real one,” says Igor Kostyukov of IAP RAS, who references their calculations on the concept of quantum electrodynamics (QED).

    2
    NASA Astrophysics

    A QED cascade is a series of processes that starts with electrons and positrons accelerating within a laser field. It will then be followed by the release of high-energy photons, electrons, and positrons.

    As high-energy photons decay, it will produce electron-positron pairs. Essentially, a QED cascade will lead to the production of electron positron high-energy photon plasmas – and while it perfectly illustrates the QED phenomenon, it is a theory that has yet to be observed under lab conditions.

    Based on this, researchers observed how intense laser pulses would interact with a foil via numerical simulations. Surprisingly, they discovered that there were more high-energy photons produced by the positrons versus electrons produced of the foil.

    And if you could produce a massive number of positrons via a corresponding experiment, you can conclude that most were generated via a QED cascade.

    As complicated as all that sounds, here’s the bottom line – this discovery can open new doors in terms of how we can efficiently and cost-effectively produce matter and antimatter, the latter of which can significantly change the way we power our spaceships.

    As has been previously noted, making this potential power source is not cheap:

    “The problem lies in the efficiency and cost of antimatter production and storage. Making 1 gram of antimatter would require approximately 25 million billion kilowatt-hours of energy and cost over a million billion dollars.”

    This work offers us a new way forward.

    Their study also offers major insight into the properties of different types of interactions that could eventually pave the way for practical applications, including the development of advanced ideas for the laser-plasma sources of high-energy photons and positrons that will exceed the brilliance of any available source we have today.

    “Next, we’re exploring the nonlinear stage when the self-generated electron-positron plasma strongly modifies the interaction,” the researchers add.

    “And we’ll also try to expand our results to more general configurations of the laser-matter interactions and other regimes of interactions – taking a wider range of parameters into consideration.”

    This article was originally published by Futurism.

    See the full article here .

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  • richardmitnick 3:04 pm on July 18, 2016 Permalink | Reply
    Tags: 3D printing could revolutionize laser design, Laser Technology,   

    From LLNL: “3D printing could revolutionize laser design” 


    Lawrence Livermore National Laboratory

    Jul. 18, 2016
    Jeremy Thomas
    thomas244@llnl.gov
    925-422-5539

    1
    Ibo Matthews inspects an in situ diagnostics test bench his team developed for studying laser-driven powder bed fusion additive manufacturing. High-speed thermal and optical mapping of the laser-powder interaction has enabled the team to reveal new physics associated with the process and helped guide high-performance computing simulations. Photo by Julie Russell.

    LLNL researchers are exploring the use of metal 3D printing to create strong, lightweight structures for advanced laser systems – an effort they say could alter the way lasers are designed in the future.

    In a Laboratory Directed Research and Development (LDRD) program, physicist Ibo Matthews and his team are experimenting with a new research-based metal 3D printer, one of only four of its kind in the world, using a customized software platform capable of unprecedented design control.

    The powder bed laser-melting printer, made by the Fraunhofer Institute for Laser Technology (ILT) and German startup Aconity 3D, was installed in December 2015. Lab engineers have added diagnostics and high-speed cameras to examine thermal emissions and to image the surface of parts as they’re being built. Matthews said the modifications will help the researchers determine how defects or deformations occur during the 3D printing process.

    “It’s very flexible; it allows us to change any of the parameters we want,” he said. “We’re developing confidence in what we’ve built. If any defects occur, it is our aim that the user can have a 3D map available at the end of the build that shows what and where it happened.”

    Matthews and his team are building on their experience in laser materials processing and interaction gained in support of both the National Ignition Facility (NIF) and directed energy projects to develop new approaches to metal 3D printing. Their work is part of an overall strategy to broaden the NIF & Photon Science (NIF&PS) laser applications portfolio and maintain core competencies in laser-matter interaction science. Moreover, NIF scientists are intrigued by the potential for the metal 3D printing platform to support lasers – not just at NIF, but in airborne systems that need to be extremely lightweight, such as those used for remote sensing and aerial scanning.

    “With precision, predictive control of 3D printing you can put the stiffness where you need it,” said Mike Carter, NIF&PS program director for Department of Defense Technologies. “You can create functionally graded structures for optical lasers and mounts that are impossible to make by conventional manufacturing methods.”

    NIF has utilized some metal parts printed at the Lab in structures for lasers. In order to use them in critical systems on a regular basis, however, researchers must be assured that each part is sound.

    To speed up the certification process, Lab engineers are attempting to shorten the development phase by taking a completely different approach – a “feed-forward” method based on computer modeling instead of trial and error. If successful, said Wayne King of LLNL’s Physical and Life Sciences Directorate, the research could fundamentally change the way metal components – including those used in optical systems – are designed and fabricated.

    “Unless you take a science-based approach to this, you won’t know why part A is different from part B,” King said. “We’re really pushing the state of the art. We’re at the beginning of seeing some applications of the technology already.”

    In the three-year LDRD project that began last year, Matthews and his team will be combining metal 3D printing with both high-fidelity optical diagnostics and high-performance computing to create more confidence in the parts they create.

    “What we’d like to do is drive this process based on simulation, and create a ‘digital fingerprint’ of certification based on optical monitoring to ensure the part is built right the first time,” Matthews said. “We’d like to be predictive, based on our physics models, to find out what we can expect with any given build and have monitoring data to show that predictions matched the outcome.”

    Matthews added that the Lab’s newest machine will go a long way toward discovering the capabilities and application of metal 3D printing for laser design.

    “It takes you from this black box to something you have control over,” he said. “It puts us two years ahead of where we would’ve been if we hadn’t bought it.”

    NIF&PS and the Lab’s Weapons and Complex Integration and Engineering directorates are jointly supporting the new printing platform.

    See the full article here .

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  • richardmitnick 10:13 am on June 28, 2016 Permalink | Reply
    Tags: , Laser Technology, , New mid-infrared laser system could detect atmospheric chemicals   

    From MIT: “New mid-infrared laser system could detect atmospheric chemicals” 

    MIT News
    MIT News
    MIT Widget

    June 28, 2016
    David L. Chandler | MIT News Office

    1
    This diagram depicts the way a mid-infrared laser (red cylinder, left) can send a beam through the atmosphere that generates filaments of ionized air molecules (multicolored beam, center, shown with magnified view). These filaments, which can be kilometers long, help to keep the beam concentrated enough to generate mid-infrared light in air (blue cloud, right) that can reveal detailed chemical composition through spectral analysis (chart at right) of the light picked up by a mid-infrared detector (bottom). Diagram courtesy of the researchers.

    Researchers at MIT and elsewhere have found a new way of using mid-infrared lasers to turn regions of molecules in the open air into glowing filaments of electrically charged gas, or plasma. The new method could make it possible to carry out remote environmental monitoring to detect a wide range of chemicals with high sensitivity.

    The new system makes use of a mid-infrared ultra-fast pulsed laser system to generate the filaments, whose colors can reveal the chemical fingerprints of different molecules. The finding is being reported this week in the journal Optica, in a paper by principal investigator Kyung-Han Hong of MIT’s Research Laboratory of Electronics, and seven other researchers at MIT; in Binghamton, New York; and in Hamburg, Germany.

    Hong explains that such filaments, as generated by lasers in the near-infrared part of the electromagnetic spectrum, have been widely studied already because of their promise for uses such as laser-based rangefinding and remote sensing. The filament phenomenon, generated by high-power lasers, serves to counter the diffraction effects that usually take place when a laser beam passes through air. When the power level reaches a certain point and the filaments are generated, they provide a kind of self-guiding channel that keeps the laser beam tightly focused.

    But it is the mid-infrared (mid-IR) wavelengths, rather than the near-IR, that offer the greatest promise for detecting a wide variety of biochemical compounds and air pollutants. Researchers who have tried to generate mid-IR filaments in open air have had little success until now, however.

    Only one previous research team has ever succeeded in generating mid-IR laser filaments in air, but it did so at a much slower rate of about 20 pulses per second. The new work — which uses 1,000 pulses per second — is the first to be carried out at the high rates needed for practical detection tools, Hong says.

    “People want to use this kind of technology to detect chemicals in the far distance, several kilometers away,” Hong says, but they have had a hard time making such systems work. One key to this team’s success is the use of a high-power femtosecond laser with pulses just 30 femtoseconds, or millionths of a billionth of a second, long. The longer the wavelength, the more laser peak power is needed to generate the desired filaments, due to stronger diffraction, he says. But the team’s femtosecond laser, coupled with what is known as a parametric amplifier, provided the necessary power for the task. This new laser system has been developed together with Franz X. Kaertner in Hamburg and other group members for last several years. At these mid-IR wavelengths, Hong says, this device produces “one of the highest peak-power levels in the world,” producing 100 gigawatts (GW, or billion watts) of peak power.

    It takes at least 45 GW of power to generate the filaments at these mid-infrared wavelengths, he says, so this device easily meets that requirement, and the team proved that it did indeed work as expected. That now opens up the potential for detecting a very wide range of compounds in the air, from a distance.

    Using spectrally broadened mid-IR laser filaments, “we can detect virtually any kind of molecule you want to detect,” Hong says, including various biohazards and pollutants, by detecting the exact color of the filament. In the mid-IR range, the absorption spectrum of specific chemicals can be easily analyzed.

    So far, the experiments have been confined to shorter distances inside the lab, but the team expects that there’s no reason the same system wouldn’t work, with further development, at much larger scales. “This is just a proof-of-principle demonstration,” Hong says.

    This research “is one of the very first investigations of self-channeling of ultraintense mid-IR laser pulses in the air,” says Pavel Polynkin, an associate research professor of optical sciences at the University of Arizona, who was not involved in this work. “Whether there will be new and exciting applications, time will show.”

    “I think there is an agreement in the ultrafast laser community that the exploration of the mid-infrared spectral domain is going to be a new frontier in ultrafast laser science,” Polynkin adds. “The extension of intense atmospheric propagation regimes into the mid-IR spectral range certainly holds a lot of promise to overcome the limitations associated with the very well-explored near-IR spectral range, namely the very unstable propagation dynamics in the near-IR. The authors tapped into a new domain of intense nonlinear optics. Without a doubt there will be follow-up work.”

    The research team also included MIT postdoc Houkun Liang; doctoral student Peter Krogen PhD ’16; alumnus Chien-Jen Lai PhD ’14; adjunct professor and group leader Franz X. Kaertner at the University of Hamburg, Germany; and Assistant Professor Bonggu Shim and his doctoral students at Binghamton University in New York. This work was funded by U.S. Air Force Office of Scientific Research.

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  • richardmitnick 8:45 am on June 14, 2016 Permalink | Reply
    Tags: , Laser Technology, , Terahertz radiation and “phase locking”   

    From MIT: “New approach to microlasers” 

    MIT News

    MIT Widget
    MIT News

    June 13, 2016
    Larry Hardesty | MIT News Office

    1
    Researchers at MIT and Sandia National Laboratories have designed a device that is an array of 37 microfabricated lasers on a single chip. Its power requirements are relatively low because the radiation emitted by all of the lasers is “phase locked,” meaning that the troughs and crests of its waves are perfectly aligned. Image courtesy of the researchers.

    Technique for “phase locking” arrays of tiny lasers could lead to terahertz security scanners.

    Terahertz radiation — the band of electromagnetic radiation between microwaves and visible light — has promising applications in security and medical diagnostics, but such devices will require the development of compact, low-power, high-quality terahertz lasers.

    In this week’s issue of Nature Photonics, researchers at MIT and Sandia National Laboratories describe a new way to build terahertz lasers that could significantly reduce their power consumption and size, while also enabling them to emit tighter beams, a crucial requirement for most practical applications.

    The work also represents a fundamentally new approach to laser design, which could have ramifications for visible-light lasers as well.

    The researchers’ device is an array of 37 microfabricated lasers on a single chip. Its power requirements are so low because the radiation emitted by all of the lasers is “phase locked,” meaning that the troughs and crests of its waves are perfectly aligned. The device represents a fundamentally new way to phase-lock arrays of lasers.

    In their paper, the researchers identified four previous phase-locking techniques, but all have drawbacks at the microscale. Some require positioning photonic components so closely together that they’d be difficult to manufacture. Others require additional off-chip photonic components that would have to be precisely positioned relative to the lasers. Hu and his colleagues’ arrays, by contrast, are monolithic, meaning they’re etched entirely from a single block of material.

    “This whole work is inspired by antenna engineering technology,” says Qing Hu, a distinguished professor of electrical engineering and computer science at MIT, whose group led the new work. “We’re working on lasers, and usually people compartmentalize that as photonics. And microwave engineering is really a different community, and they have a very different mindset. We really were inspired by microwave-engineer technology in a very thoughtful way and achieved something that is totally conceptually new.”

    Staying focused

    The researchers’ laser array is based on the same principle that underlies broadcast TV and radio. An electrical current passing through a radio antenna produces an electromagnetic field, and the electromagnetic field induces a corresponding current in nearby antennas. In Hu and his colleagues’ array, each laser generates an electromagnetic field that induces a current in the lasers around it, which synchronizes the phase of the radiation they emit.

    This approach exploits what had previously been seen as a drawback in small lasers. Chip-scale lasers have been an active area of research for decades, for potential applications in chip-to-chip communication inside computers and in environmental and biochemical sensing. But as the dimensions of a laser shrink, the radiation the laser emits becomes more diffuse. “This is nothing like a laser-beam pointer,” Hu explains. “It really radiates everywhere, like a tiny antenna.”

    If a chip-scale laser is intended to emit radiation in one direction, then any radiation it emits in lateral directions is wasted and increases its power consumption. But Hu and his colleagues’ design recaptures that laterally emitted radiation.

    In fact, the more emitters they add to their array, the more laterally emitted radiation is recaptured, lowering the power threshold at which the array will produce laser light. And because the laterally emitted radiation can travel long distances, similar benefits should accrue as the arrays grow even larger.

    “I’m a firm believer that all physical phenomena can be pros or cons,” Hu says. “You can’t just say unequivocally that such-and-such a behavior is universally a good or bad thing.”

    Tightening up

    In large part, the energy from the recaptured lateral radiation is re-emitted in the direction perpendicular to the array. So the beam emitted by the array is much tighter than that emitted by other experimental chip-scale lasers. And a tight beam is essential for most envisioned applications of terahertz radiation.

    In security applications, for instance, terahertz radiation would be directed at a chemical sample, which would absorb some frequencies more than others, producing a characteristic absorption fingerprint. The tighter the beam, the more radiation reaches both the sample and, subsequently, a detector, yielding a clearer signal.

    Hu is joined on the paper by first author Tsung-Yu Kao, who was an MIT graduate student in electrical engineering when the work was done and is now chief technology officer at LongWave Photonics, a company that markets terahertz lasers, and by John Reno of Sandia National Laboratories.

    “The use of phased arrays of antennas is widespread in the microwave and allows one to direct radiation in a very narrow beam, in a specific direction,” says Benjamin Williams, an associate professor of electrical engineering at the University of California at Los Angeles. “In the microwave, however, it is straightforward to drive each antenna with the same phase so that all the contributions to the field add up constructively in the far field. It is more complicated to do the same thing using an array of laser emitters, since you can’t easily control the phase of each element. Rather, you must coax each laser emitter to phase-lock with its neighbors through some mechanism. This work has shown a new method to phase-lock large arrays of lasers.”

    “The work is also important for addressing an ongoing challenge for terahertz QC [quantum cascade] lasers, namely, how can you generate a high-quality beam with good efficiency?” he adds. “This has traditionally been tough for terahertz QC lasers, since the individual laser cavities are smaller than the wavelength. It turns out that this fact means you can borrow many of the techniques from the microwave — like phased-array antennas. The work shows a high-quality beam with very high slope efficiency in a monolithic surface-emitting package.”

    See the full article here .

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  • richardmitnick 2:57 pm on June 8, 2016 Permalink | Reply
    Tags: , Laser Technology, patent new class of lasers, , Researchers invent   

    From phys.org: “Researchers invent, patent new class of lasers” 

    physdotorg
    phys.org

    June 8, 2016
    No writer credit found

    1
    Kristan Corwin, left, and Brian Washburn, both associate professors of physics at Kansas State University, have invented a new patented class of lasers. Credit: Kansas State University

    A new class of lasers developed by a team that included physics researchers at Kansas State University could help scientists measure distances to faraway targets, identify the presence of certain gases in the atmosphere and send images of the earth from space.

    These energy-efficient lasers also are portable, produce light at difficult-to-reach wavelengths and have the potential to scale to high-powered versions.

    The new lasers were invented by Brian Washburn and Kristan Corwin, both associate professors of physics at Kansas State University’s College of Arts & Sciences, along with Andrew Jones, a May 2012 doctoral graduate in physics, and Rajesh Kadel, a May 2014 doctoral graduate in physics. Other contributors include three University of New Mexico physics and astronomy researchers: Wolfgang Rudolf, a Regents professor and department chair, Vasudevan Nampoothiri, a research assistant professor, and Amarin Ratanavis, a doctoral student; and John Zavada, a Virginia-based optic and photonic physicist who brought them all together.

    The new lasers are fiber-based and use various molecular gases to produce light. They differ from traditional glass-tube lasers, which are large and bulky, and have mirrors to reflect the light. But the novel lasers use a hollow fiber with a honeycomb structure to hold gas and to guide light. This optical fiber is filled with a molecular gas, such as hydrogen cyanide or acetylene. Another laser excites the gas and causes a molecule of the excited gas to spontaneously emit light. Other molecules in the gas quickly follow suit, which results in laser light.

    “By putting the gas in a hollow core, we can have really high intensities of light without having to put such high amounts of power into the laser,” Corwin said. “If you had a glass tube of that size and put light in it, the light would escape through the sides. It’s actually the structure that makes it work.”

    The structure also allows for portability. In contrast to traditional lasers, which are fragile and cumbersome to move, the researchers’ more durable fiber laser is about the thickness of a single strand of hair and can wrap around itself for compact storage and transportation.

    “The smallness is nice,” Washburn said. “You can wrap up the coil like a string.”

    The invention process began when Zavada brought Washburn and Corwin, who already had expertise putting gas into hollow fibers, together with Rudolph and Nampoothiri, who were skilled in making optically pumped gas lasers.

    “We thought hard about how this would all work together, and after about a year and a half, we came up with this,” Corwin said.

    The inventors’ lasers use gas, which was the popular method before manufacturers moved to solid-state materials. For example, up until the mid-1990s, grocery store scanners were gas lasers, while present-day grocery scanners use solid-state lasers.

    “What we’ve done is use an old-school technology medium in a new-school package,” Washburn said.

    The researchers are continuing to study and improve the lasers using fibers from Fetah Benabid at Xlim in Limoges, France, with funding from the U.S. Air Force Office of Scientific Research and the U.S. Air Force Research Laboratory.

    See the full article here .

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    Phys.org™ (formerly Physorg.com) 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, Phys.org’s readership has grown steadily to include 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.

     
  • richardmitnick 3:40 pm on June 6, 2016 Permalink | Reply
    Tags: , Laser Technology, Scientists Use a Frozen Gas to Boost Laser Light to New Extremes,   

    From SLAC: “Scientists Use a Frozen Gas to Boost Laser Light to New Extremes” 


    SLAC Lab

    June 6, 2016

    1
    For the experiment, Stanford graduate student Georges Ndabashimiye had to figure out how to freeze argon gas into a thin layer inside a small vacuum chamber chilled to 20 kelvins – close to absolute zero. (SLAC National Accelerator Laboratory)

    SLAC/Stanford Study Opens a Path to Creating Attosecond Laser Pulses by Inducing ‘High Harmonic Generation’ in a Solid

    To observe something as small and fast as an electron rushing to form a chemical bond, you need a bright light with an incredibly small wavelength that comes in very fast pulses – just a few attoseconds, or billionths of a billionth of a second, long.

    Scientists figured out more than a decade ago how to make this specialized form of light through a process known as “high harmonic generation,” or HHG, which shifts laser light to much shorter wavelengths and shorter pulses by shining it through a cloud of gas.

    Now researchers at the Department of Energy’s SLAC National Accelerator Laboratory, Stanford University and Louisiana State University have achieved an even more dramatic HHG shift by shining an infrared laser through argon gas that’s been frozen into a thin, fragile solid whose atoms barely cling to each other.

    The laser light that emerged from the frozen gas was in the extreme ultraviolet range, with wavelengths about 40 times shorter than the light that went in, they report today in the journal Nature.

    The results give researchers a potential new, solid-state tool for “attosecond science,” which explores processes like the motions of electrons in atoms and the natural vibrations of molecules.

    And in the longer term, they could lead to bright, ultrafast, short-wavelength lasers that are much more compact, and perhaps even electronic devices that operate millions of times faster than current technology, says David Reis, a co-author of the report and deputy director of the Stanford PULSE Institute, a joint institute of SLAC and Stanford.

    Making the First Key Comparisons

    “Now, for the first time, we are able to directly compare how high harmonic generation works in the solid and gaseous forms of a single element. We did this in both argon and krypton,” Reis said.

    “These comparisons should allow us to resolve a number of outstanding questions – for instance, what, exactly, is the effect of packing the atoms closer together? In our study it seemed to enhance the HHG process. We expect that these results, and follow-up studies that are already underway, will give us a much better understanding of the fundamental physics.”

    High harmonic generation is far from new. Discovered in the late 1980s, it offers a way to produce laser-like bursts of light at far higher frequencies and shorter wavelengths than a laser can generate directly. But only in the past decade has it been developed into a readily accessible tool for exploring the attosecond realm.

    Today scientists generally use argon gas as the medium for generating attosecond laser pulses with HHG. Laser light shining on the gas liberates electrons from all the argon atoms it hits. The electrons fly away, loop back and reconnect with their home atoms all at the same time. This reconnection generates attosecond bursts of light that combine to form an attosecond laser pulse.

    Tricky Work with Fragile Crystals

    In 2010, a PULSE team led by Reis and SLAC staff scientist Shambhu Ghimire reported the first observation of HHG in a crystal ­– zinc oxide, a semiconducting material that is probably most familiar as a white powder in sunscreens.

    But it was difficult to compare how HHG proceeds in this complex solid to what happens in a gas. So in 2011 they began a series of experiments to directly compare HHG in gaseous and solid argon.

    “This is a conceptually simple but technically very challenging experiment,” Ghimire says. “Argon crystals are extremely, extremely fragile, and the reason they’re fragile is that the interaction between the atoms is very weak. But this was just what we wanted – something that looked just like a gas, but at higher density.”

    The work of performing the experiment and analyzing the data fell to Georges Ndabashimiye, a graduate student at PULSE and the Stanford Department of Applied Physics, who had to figure out how to freeze argon gas into a thin layer inside a small vacuum chamber chilled to 20 kelvins – close to absolute zero.

    Ndabashimiye says he had to be patient with the challenging process. “I didn’t really know how it was going to turn out, but it kept working and I found I could do more and learn more. That was quite exciting,” he says.

    Looking Toward Potential Applications

    When used to perform HHG, the argon crystal reduced the wavelength of incoming laser light 40-fold, compared to 20-fold in argon gas hit with the same level of illumination. Consequently, it also produced a laser beam of much higher energy – 40 electronvolts, versus 25 electronvolts in argon gas.

    Packing the atoms closer together appears to produce higher harmonics than using single, widely spaced atoms, the researchers said, and working with these frozen gases should help them figure out why.

    There are also many commonalities between the behavior in gases and solids, which leads them to believe that techniques developed for working with gases can be applied to solids, too.

    “If a wide range of different types of solids can produce these attosecond pulses, we might be able to engineer the right solid with the right properties for things like inspecting semiconductor chips and masks, developing new types of microscopy and mapping out how electrons behave inside solids,” Reis said.

    Theorists at Louisiana State University also contributed to the research, which was funded by the DOE Office of Science and the National Science Foundation. The research team also used SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), a DOE Office of Science User Facility, to measure the quality of the frozen argon crystals.

    Citation: G. Ndabashimiye et al., Nature, 6 June 2016 (10.1038/nature17660).

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    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.
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