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  • richardmitnick 4:53 pm on October 8, 2014 Permalink | Reply
    Tags: , Laser Technology,   

    From LLNL: “LLNL to play key role in 10 petawatt laser project” 


    Lawrence Livermore National Laboratory

    10/08/2014
    Breanna Bishop, LLNL, (925) 423-9802, bishop33@llnl.gov

    Lawrence Livermore National Laboratory has once again been selected to support the development and construction of an ultra-intense laser system for the European Union’s Extreme Light Infrastructure Beamlines (ELI-Beamlines) in the Czech Republic.

    beam
    3D CAD rendering of the 10PW laser system. Credit: National Energetics Inc.

    A consortium led by National Energetics Inc., in partnership with Ekspla UAB, was awarded the contract to construct the system, which will be the most powerful laser of its class in the world, capable of producing peak power in excess of 10 petawatts (PW). Due to LLNL’s long-standing expertise in laser research and development, the consortium selected the Laboratory for a $3.5 million subcontract to support development of this system.

    “The award of this project is another clear statement of the internationally leading nature of LLNL’s laser design capability,” said Mike Dunne, LLNL’s director of laser fusion energy. “It also is another great example of where LLNL is helping move forward the global state-of-the-art of high power lasers, working collaboratively with the U.S. and European industry and academia. We are very excited to work with the National Energetics consortium, which has a very compelling approach to reaching the 10 petawatt goal.”

    Under the subcontract, LLNL will be responsible for: contributing to the physics design of the liquid-cooled laser amplifier, allowing it to get to the high energies required for accessing 10 PW power; contributing to the physics and engineering design of the short pulse compressor, which takes the high energy beam and compresses it to the required pulse length; and production of the large aperture diffraction gratings for this compressor.

    This system will be one of the four major beamlines at the new ELI-Beamlines facility. In addition to work on this beamline, LLNL also is responsible for the design, development and installation of a second beamline at the facility, through a more than $45 million contract awarded in 2013. When commissioned to its full design performance, the laser system, called the “High repetition-rate Advanced Petawatt Laser System” (HAPLS), will be the world’s highest average power PW laser system. The two systems will thus offer a highly attractive capability for the new ELI-Beamlines facility, which will appeal to academic and industrial researchers from across the world.

    See the full article here.

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  • richardmitnick 3:58 pm on September 17, 2014 Permalink | Reply
    Tags: , Laser Technology,   

    From physicsworld: “New plasmonic nanolaser is cavity-free” 

    physicsworld
    physicsworld.com

    Sep 17, 2014
    Tim Wogan

    A new design for a cavity-free nanolaser has been proposed by physicists at Imperial College London. The design builds on a proposal from the same team earlier this year to reduce the group velocity of light of a particular frequency to exactly zero in a metal–dielectric–metal waveguide. The laser, which has yet to be built, makes use of two such zero-velocity regions, and would achieve population inversion and create a laser beam without the need for an optical cavity. The researchers suggest that the design could have important applications in optical telecommunications and computing, as well as theoretical implications in reconciling the physics of lasers with plasmonics.

    graph
    Slowing light to a stop: nanolaser has no cavity

    The traditional design for a laser involves encasing a gain medium such as a gas in a cavity containing two opposing mirrors. The gain medium contains two electronic energy levels, and, in the natural state, the lower energy level is the more populated. However, by injecting electrical or light energy into the cavity, some electrons can be “pumped” into the upper state. At low pumping levels, atoms pushed to the upper level decay spontaneously back to the ground state with the emission of a photon. However, above a certain threshold, transitions back to the ground state are predominantly caused by an excited atom’s absorption of a second photon. The two photons are emitted perfectly in phase, and go on to excite emission from more atoms. The resulting beam of phase-coherent photons is the laser beam.

    Lasers have revolutionized modern science and technology, with tiny lasers can be found everywhere from cheap pointers to state-of-the-art telecommunications systems. While much smaller nanoscale lasers would be useful for creating chip-based optical circuits, the need for a cavity limits means that it is difficult to miniaturize a conventional laser beyond the wavelength of the light it produces. This limit is about one micron for the light used in telecommunications technologies.

    Plasmonic interactions

    Now, Ortwin Hess and colleagues have devised a new way of producing a sub-wavelength laser by removing the cavity altogether. The researchers designed a layered metal–dielectric–metal waveguide structure that supports plasmonic interactions between light and conduction electrons at the metal–dielectric interfaces. Such a plasmonic waveguide supports two “zero-velocity singularities” at closely spaced but distinct frequencies. Light of other frequencies will propagate through the semiconductor very slowly – allowing it plenty of time to interact with the gain material. While slow and stopped light might sound like unphysical concepts, they can occur when light interacts with plasmons. Injecting a pulse of this slow light, the researchers calculated, will pump carriers from a lower energy state to a higher state. This higher state would then decay to an intermediate state, which would then decay to produce the laser light. The presence of the zero-velocity singularities causes the laser light to be trapped in the material, where it drives the desired coherent stimulated emission.

    To produce a laser beam, however, some of the laser light must be able to leave the device. In previous work (see “Plasmonic waveguide stops light in its tracks”), Hess and colleagues proposed exciting a zero-velocity mode by passing the light through the cladding in the form of an evanescent wave – a special type of wave the frequency of which is a complex number. Radiation incident on the cladding would excite an evanescent wave, which would in turn excite the stopped-light mode in the dielectric inside. In their new paper, Hess and colleagues turn this idea on its head and use the evanescent field to allow laser light to escape. By varying the precise properties and thickness of the cladding layer, the proportion of light allowed to escape could be tuned, producing a laser beam of variable intensity.

    Biomedical applications

    Nicholas Fang, a nanophotonics expert at the Massachusetts Institute of Technology, believes that, if such cavity-free nanolasers could be produced, they could have major practical implications not only in computation and signalling, but also in less-obvious fields such as prosthetics: he suggests they could be embedded in synthetic tissue to provide sensors with output signals detectable by the nervous system. “Here you’d have a laser source that could be directly implantable,” he explains.

    Hess, meanwhile, is excited by the potential theoretical implications of the work. While the current research focuses on using plasmonic interactions to produce coherent light, he believes that it should also be possible to keep the plasmons themselves confined within the waveguide to produce a miniature surface plasmon laser or “spaser”.

    The research is described in Nature Communications.

    See the full article here.

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

    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.
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  • richardmitnick 3:41 pm on August 27, 2014 Permalink | Reply
    Tags: , ELI-Beamlines, Laser Technology, ,   

    From Livermore Lab: “LLNL synchs up with ELI Beamlines on timing system” 


    Lawrence Livermore National Laboratory

    08/27/2014
    Breanna Bishop, LLNL, (925) 423-9802, bishop33@llnl.gov

    In 2013, Lawrence Livermore National Laboratory (LLNL), through Lawrence Livermore National Security LLC (LLNS), was awarded more than $45 million to develop and deliver a state-of-the-art laser system for the European Union’s Extreme Light Infrastructure Beamlines facility (ELI-Beamlines), under construction in the Czech Republic.

    two
    Thomas Manzec and Marc-Andre Drouin, from ELI Beamlines, work on synchronizing the HAPLS and ELI timing systems. Photo by Jim Pryatel.

    eli
    The ELI Beamlines facility is being built on a brownfield site with sufficient infrastructure. According to the current zoning plan, the area can be used for public amenities, science and research. It is therefore a place that provides enough space both for the laser center, as well as for any other building of similar use (technology park buildings, spin-off companies or other research facilities).

    When commissioned to its full design performance, the laser system, called the “High repetition-rate Advanced Petawatt Laser System” (HAPLS), will be the world’s highest average power petawatt laser system.

    HAPLS
    HAPLS

    Nearly a year into the project, much progress has been made, and all contract milestones to date have been delivered on schedule. Under the same agreement, ELI Beamlines delivers various work packages to LLNL enabling HAPLS control and timing systems to interface with the overarching ELI Beamlines facility control system. In a collaborative effort, researchers and engineers from LLNL’s NIF & Photon Science Directorate work with scientists from the ELI facility to develop, program and configure these systems.

    National Ignition Facility
    NIF at Livermore

    According to Constantin Haefner, LLNL’s project manager for HAPLS, this joint work is vital. “Working closely together on these collaborative efforts allows us to deliver a laser system most consistent with ELI Beamlines facility requirements. It also allows the ELI-Beamlines team to gain early insight into the laser system architecture and gain operational experience,” he said.

    This summer, that process began. Marc-Andre Drouin and Karel Kasl, control system programmers for ELI, spent three months at LLNL working with the HAPLS integrated control system team. During their time at LLNL, they focused almost exclusively on the ELI-HAPLS timing interface, which allows exact synchronization of HAPLS to the ELI Beamlines master clock.

    “The HAPLS timing system must be able to operate independent of the ELI timing system,” Drouin said. “But, it also needs to be capable of being perfectly synchronized to ELI. That bridge between timing systems is what we have been working on – making sure HAPLS runs very well independently as well as integrating with ELI.”

    Haefner pointed out that while HAPLS is a major component, it becomes a subsystem when it moves to the ELI facility. Once at ELI, HAPLS will integrate with the wider user facility, consisting of target systems, experimental systems, diagnostic systems – all of which have to be timed and fed from a master clock.

    Kasl likened the master clock to a universal clock used by an office. “We brought the clock here, and now everyone in the office is using the clock to synchronize their work,” he said.

    The master clock, built by ELI, was programmed as a bridge between the ELI and HAPLS timing systems. During their time at LLNL, Drouin and Kasl worked on configuring that hardware and writing the software that talks to the clock and to the subcomponents that control a very precise sequence of events.

    Last week, the ELI team finished their three-month stint at LLNL, but will be back in early fall to continue work – and they’re looking forward to it.

    “This unit is going to get integrated with our other systems, so there needs to be an overlap between the two teams,” Kasl said.

    “It’s good experience for us to learn about the internal workings of the HAPLS system,” Drouin added. “Having this inside knowledge of the most integral parts of the laser is a very big advantage for us in the long run.”

    Earlier this year, Jack Naylon and Tomas Mazanec, also from ELI, visited LLNL to contribute to the work.

    See the full article here.

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  • richardmitnick 3:28 pm on August 23, 2014 Permalink | Reply
    Tags: , , Laser Technology, Electrical Engineering,   

    From Princeton: “Laser device may end pin pricks, improve quality of life for diabetics” 

    Princeton University
    Princeton University

    August 20, 2014
    John Sullivan, Office of Engineering Communications

    Princeton University researchers have developed a way to use a laser to measure people’s blood sugar, and, with more work to shrink the laser system to a portable size, the technique could allow diabetics to check their condition without pricking themselves to draw blood.

    “We are working hard to turn engineering solutions into useful tools for people to use in their daily lives,” said Claire Gmachl, the Eugene Higgins Professor of Electrical Engineering and the project’s senior researcher. “With this work we hope to improve the lives of many diabetes sufferers who depend on frequent blood glucose monitoring.”

    In an article published June 23 in the journal Biomedical Optics Express, the researchers describe how they measured blood sugar by directing their specialized laser at a person’s palm. The laser passes through the skin cells, without causing damage, and is partially absorbed by the sugar molecules in the patient’s body. The researchers use the amount of absorption to measure the level of blood sugar.

    Sabbir Liakat, the paper’s lead author, said the team was pleasantly surprised at the accuracy of the method. Glucose monitors are required to produce a blood-sugar reading within 20 percent of the patient’s actual level; even an early version of the system met that standard. The current version is 84 percent accurate, Liakat said.

    “It works now but we are still trying to improve it,” said Liakat, a graduate student in electrical engineering.

    team
    A new system developed by Princeton researchers uses a laser to allow diabetics to check their blood sugar without pricking their skin. Members of the research team included, from left, Sabbir Liakat, a graduate student in electrical engineering; Claire Gmachl, the Eugene Higgins Professor of Electrical Engineering; and Kevin Bors, who graduated in 2013 with a degree in electrical engineering. (Photos by Frank Wojciechowski for the Office of Engineering Communications)

    When the team first started, the laser was an experimental setup that filled up a moderate-sized workbench. It also needed an elaborate cooling system to work. Gmachl said the researchers have solved the cooling problem, so the laser works at room temperature. The next step is to shrink it.

    “This summer, we are working to get the system on a mobile platform to take it places such as clinics to get more measurements,” Liakat said. “We are looking for a larger dataset of measurements to work with.”

    The key to the system is the infrared laser’s frequency. What our eyes perceive as color is created by light’s frequency (the number of light waves that pass a point in a certain time). Red is the lowest frequency of light that humans normally can see, and infrared’s frequency is below that level. Current medical devices often use the “near-infrared,” which is just beyond what the eye can see. This frequency is not blocked by water, so it can be used in the body, which is largely made up of water. But it does interact with many acids and chemicals in the skin, so it makes it impractical to use for detecting blood sugar.

    Mid-infrared light, however, is not as much affected by these other chemicals, so it works well for blood sugar. But mid-infrared light is difficult to harness with standard lasers. It also requires relatively high power and stability to penetrate the skin and scatter off bodily fluid. (The target is not the blood but fluid called dermal interstitial fluid, which has a strong correlation with blood sugar.)

    The breakthrough came from the use of a new type of device that is particularly adept at producing mid-infrared frequencies — a quantum cascade laser.

    device
    The new monitor uses a laser, instead of blood sample, to read blood sugar levels. The laser is directed at the person’s palm, passes through skin cells and is partially absorbed by sugar molecules, allowing researchers to calculate the level of blood sugar.

    In many lasers, the frequency of the beam depends on the material that makes up the laser — a helium-neon laser, for example, produces a certain frequency band of light. But in a quantum cascade laser, in which electrons pass through a “cascade” of semiconductor layers, the beam can be set to one of a number of different frequencies. The ability to specify the frequency allowed the researchers to produce a laser in the mid-infrared region. Recent improvements in quantum cascade lasers also provided for increased power and stability needed to penetrate the skin.

    To conduct their experiment, the researchers used the laser to measure the blood sugar of three healthy people before and after they each ate 20 jellybeans, which raise blood sugar levels. The researchers also checked the measurements with a finger-prick test. They conducted the measurements repeatedly over several weeks.

    The researchers said their results indicated that the laser measurements readings produced average errors somewhat larger than the standard blood sugar monitors, but remained within the clinical requirement for accuracy.

    “Because the quantum cascade laser can be designed to emit light across a very wide wavelength range, its usability is not just for glucose detection, but could conceivably be used for other medical sensing and monitoring applications,” Gmachl said.

    Besides Liakat and Gmachl, researchers included Kevin Bors, Class of 2013, Laura Xu, Class of 2015, and Callie Woods, Class of 2014, who worked on the project as undergraduate students majoring in electrical engineering; and Jessica Doyle, a teacher at Hunterdon Regional Central High School.

    Support for the research was provided in part by the Wendy and Eric Schmidt Foundation, the National Science Foundation, Daylight Solutions Inc., and Opto-Knowledge Systems. The research involving human subjects was conducted according to regulations set by the Princeton University Institutional Review Board.

    See the full article here.

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    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

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  • richardmitnick 10:12 am on August 7, 2014 Permalink | Reply
    Tags: , Laser Technology, ,   

    From Slac Lab: “Catching Chemistry in Motion” 


    SLAC Lab

    August 6, 2014
    Laser-timing Tool Works at the Speed of Electrons

    Researchers at the Department of Energy’s SLAC National Accelerator Laboratory have developed a laser-timing system that could allow scientists to take snapshots of electrons zipping around atoms and molecules. Taking timing to this new extreme of speed and accuracy at the Linac Coherent Light Source X-ray laser, a DOE Office of Science user facility, will make it possible to see the formative stages of chemical reactions.

    “Previously, we could see a chemical bond before it’s broken and after it’s broken,” said Ryan Coffee, an LCLS scientist whose team developed this system. “With this tool, we can watch the bond while it is breaking and ‘freeze-frame’ it.”

    The success of most LCLS experiments relies on precise timing of the X-ray laser with another laser, a technique known as “pump-probe.” Typically, light from an optical laser “pumps” or triggers a specific effect in a sample, and researchers vary the arrival of the X-ray laser pulses, which serve as the “probe” to capture images and other data that allow them to study the effects at different points in time.

    Pump-probe experiments at LCLS are used to study a wide range of processes at the atomic or molecular scale, including studies of biological samples and exotic materials like high-temperature superconductors.

    But LCLS X-ray pulses are tricky to control. They have inherent jitter that causes them to fluctuate in arrival time, energy, position, duration and the wavelength of their light.

    There are several tools and techniques that scientists use to understand and limit the impacts of jitter on experiments, and timing tools counter the arrival-time jitter by offering very precise measurements. These measurements can help scientists to interpret their data by pinpointing the timing of changes they see in samples after they are exposed to the first laser pulse. Some experiments would not be possible without precise timing tools because of the ultrafast scale of the changes they are trying to observe.

    Achieving ‘Attosecond’ Experiments

    tool
    An illustration of the setup used to test an “attosecond” timing tool at SLAC’s Linac Coherent Light Source X-ray laser. The dashed line, produced by an algorithm that analyzes the colorized spectrograph image (bottom) represents the arrival time of the X-ray laser. (Ryan Coffee and Nick Hartmann/SLAC)

    Timing tools now in place at most LCLS experimental stations can measure the arrival time of the optical and X-ray laser pulses to an accuracy within 10 femtoseconds, or quadrillionths of a second. The new pulse-measuring system, which is highlighted in the July 27 edition of Nature Photonics, builds upon the existing tools and pushes timing to attoseconds, which are quintillionths (billion-billionths) of a second.

    anime
    This animation shows a sequence of spectrograph images used to precisely measure arrival time of X-rays relative to optical laser pulses at SLAC’s LCLS. The upper edge of the dark blue pattern represents the arrival time of the X-ray laser pulse. The scale at left measures the relative delay of X-ray and optical laser pulses, and the bottom measures the wavelength of the transmitted optical light. (Nick Hartmann/SLAC)

    Nick Hartmann, an LCLS research associate and doctoral student at the University of Bern in Switzerland who is the lead author of the study detailing the system, said, “An X-ray laser with attosecond timing resolution would open up a new class of experiments on the natural time scale of electron motion.”

    The new system uses a high-resolution spectrograph, a type of camera that records the timing and wavelength of the probe laser pulses. The colorful patterns it displays represent the different wavelengths of light that passed, at slightly different times, through a thin sample of silicon nitride.

    This material experiences a cascading reaction in its electrons when it is struck by an X-ray pulse. This effect leaves a brief imprint in the way light passes through the sample, sort of like a temporary interruption of vision following a camera’s flash.

    This X-ray-caused effect shows up in the way the light from the other laser pulse passes through the silicon nitride – it is seen as a brief dip in the amount of light recorded by the spectrograph, like the after-image of a camera flash. An image-analysis algorithm then precisely calculates, based on the recorded patterns, the relative arrival time of the X-ray pulses.

    The new timing system is designed to avoid distortion effects caused by some other timing tools and to work reliably with a variety of focusing and filtering tools. It can provide real-time readouts of laser arrival times and jitter to benefit experiments in progress, and can be added to existing timing setups at LCLS.

    Hartmann said additional innovations could expand the applications of the new system: “We are putting the parts together to allow attosecond experiments at LCLS and other X-ray lasers like it.”

    three
    hese three panels show different types of jitter, or fluctuations, in the X-ray laser pulses produced at SLAC’s Linac Coherent Light Source. The left panel shows how the X-ray beam fluctuates in its direction. The middle panel shows how the spectrum (wavelength or “color”) of the X-ray laser changes randomly from pulse to pulse. The right panel shows the X-ray-caused dip in the amount of light being recorded. (SLAC)

    See the full article here.

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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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  • richardmitnick 8:06 pm on July 17, 2014 Permalink | Reply
    Tags: , , , Laser Technology, ,   

    From SLAC Lab: “X-ray Laser Measures Leaping Electrons” 


    SLAC Lab

    July 17, 2014
    SLAC Experiment Provides New Insight About How Electrons Move Across Molecules

    Many chemical reactions – such as those at work in batteries and photosynthesis – rely on electrons moving from one atom or molecule to another. Now, scientists have directly measured the movement of electrons as they leap across parts of the same molecule, which provides useful insight about the mechanisms involved in forming and breaking chemical bonds.

    The experiment took place at SLAC’s Linac Coherent Light Source (LCLS) X-ray laser, a DOE Office of Science user facility. Scientists split molecules with pulses of infrared light and then hit them with intense X-ray pulses to drive and study the transfer of electrons between the fragments. The experiment showed that the electrons can travel surprisingly long distances – up to 10 times the length of the original, intact molecule – to jump the gap. The results are published in the July 18 issue of Science.

    “This is a clean example of a very important charge-transfer process that can only be resolved using a tool like LCLS,” said Artem Rudenko of Kansas State University, who led the experiment. The knowledge gained in the experiment may ultimately help to explain mechanisms of electron transfer in more complex molecules, including biological samples. This is also central to understanding how X-rays can damage samples and obscure X-ray images.

    As a basic form of chemical reaction, electron transfer is vital to many life processes. The 1992 Nobel Prize in Chemistry recognized pioneering theoretical work in electron transfer that has underpinned many related chemistry experiments.

    The team studied methyl iodide molecules, also known as iodomethane, which break in a predictable way when hit by intense infrared light: One fragment contains a single iodine atom, the other has carbon and hydrogen atoms.

    iodide
    In this illustration of a severed methyl iodide molecule, electrons jump the gap from one fragment containing carbon and hydrogen atoms (right) to the other fragment, which contains an iodine atom (left). Researchers used SLAC’s Linac Coherent Light Source X-ray laser to stimulate and measure the electron-transfer process. (SLAC National Accelerator Laboratory) “>In this illustration of a severed methyl iodide molecule, electrons jump the gap from one fragment containing carbon and hydrogen atoms (right) to the other fragment, which contains an iodine atom (left). Researchers used SLAC’s Linac Coherent Light Source X-ray laser to stimulate and measure the electron-transfer process. (SLAC National Accelerator Laboratory)

    They tuned the LCLS X-ray pulses to knock out electrons only from the iodine atoms, creating a positive charge that attracts electrons from the other fragment to fill the vacancies. As the fragments drift, the gap that electrons jump to reach the iodine atoms widens until it becomes too far for them to reach.

    The researchers varied the timing of the X-ray pulses to tune the distance electrons had to jump to cross this gap. They used time- and position-sensitive detectors to determine the final charge and energy of the fragments, which told them where the remaining electrons ended up. While LCLS X-ray laser pulses are ultrashort, lasting just quadrillionths of a second, or femtoseconds, the electron-transfer process typically spans less than a single femtosecond, Rudenko noted. During this very short time, the distance between the fragments does not change, allowing researchers to more easily gauge the electron movement.

    “With each pair of infrared and X-ray pulses we tried to look at just one molecule,” said Benjamin Erk of Germany’s DESY lab, who analyzed the data. “We traced essentially all of the fragments produced to give us a microscopic ‘picture’ of a single fracture event.” Researchers collected data from about 800,000 fractured molecules.

    The same team, which was also led by Daniel Rolles of DESY, has already conducted follow-up research on other molecules at LCLS, and researchers said it may be possible to study biological compounds found in DNA and RNA, as an example, using the same method. They hope to directly measure the time it takes for the electrons to move across larger and more complex molecules, Rudenko said.

    In addition to researchers from Kansas State University, DESY and SLAC, other collaborating researchers were from the Center for Free-Electron Laser Science, Max Planck Institute for Nuclear Physics, Max Planck Institute for Medical Research, University of Hamburg and Physikalisch-Technische Bundesanstalt (National Metrology Institute), all in Germany; and from Sorbonne University and the French National Center for Scientific Research in France.

    The work was supported by the Max Planck Society, which funded the development and operation of the CAMP instrument used in the experiment; the U.S. Department of Energy Office of Science; the Kansas NSF EPSCoR “First Award” program; the Young Investigator Program of the Helmholtz Association; and the German Research Foundation’s Hamburg Center for Ultrafast Imaging – Structure, Dynamics and Control of Matter at the Atomic Scale.

    See the full article here.

    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.
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  • richardmitnick 7:46 pm on July 17, 2014 Permalink | Reply
    Tags: , , Laser Technology, Quartz technology   

    From Caltech: “Future Electronics May Depend on Lasers, Not Quartz” 

    Caltech Logo
    Caltech

    07/17/2014
    Jessica Stoller-Conrad

    Nearly all electronics require devices called oscillators that create precise frequencies—frequencies used to keep time in wristwatches or to transmit reliable signals to radios. For nearly 100 years, these oscillators have relied upon quartz crystals to provide a frequency reference, much like a tuning fork is used as a reference to tune a piano. However, future high-end navigation systems, radar systems, and even possibly tomorrow’s consumer electronics will require references beyond the performance of quartz.

    three
    Vahala’s new laser frequency reference (left) is a small 6 mm disk; the quartz “tuning fork” (middle) is the frequency reference commonly used today in wristwatches to set the second. The dime (right) is for scale.
    Credit: Jiang Li/Caltech

    Now, researchers in the laboratory of Kerry Vahala, the Ted and Ginger Jenkins Professor of Information Science and Technology and Applied Physics at Caltech, have developed a method to stabilize microwave signals in the range of gigahertz, or billions of cycles per second—using a pair of laser beams as the reference, in lieu of a crystal.

    Quartz crystals “tune” oscillators by vibrating at relatively low frequencies—those that fall at or below the range of megahertz, or millions of cycles per second, like radio waves. However, quartz crystals are so good at tuning these low frequencies that years ago, researchers were able to apply a technique called electrical frequency division that could convert higher-frequency microwave signals into lower-frequency signals, and then stabilize these with quartz.

    The new technique, which Vahala and his colleagues have dubbed electro-optical frequency division, builds off of the method of optical frequency division, developed at the National Institute of Standards and Technology more than a decade ago. “Our new method reverses the architecture used in standard crystal-stabilized microwave oscillators—the ‘quartz’ reference is replaced by optical signals much higher in frequency than the microwave signal to be stabilized,” Vahala says.

    Jiang Li—a Kavli Nanoscience Institute postdoctoral scholar at Caltech and one of two lead authors on the paper, along with graduate student Xu Yi—likens the method to a gear chain on a bicycle that translates pedaling motion from a small, fast-moving gear into the motion of a much larger wheel. “Electrical frequency dividers used widely in electronics can work at frequencies no higher than 50 to 100 GHz. Our new architecture is a hybrid electro-optical ‘gear chain’ that stabilizes a common microwave electrical oscillator with optical references at much higher frequencies in the range of terahertz or trillions of cycles per second,” Li says.

    The optical reference used by the researchers is a laser that, to the naked eye, looks like a tiny disk. At only 6 mm in diameter, the device is very small, making it particularly useful in compact photonics devices—electronic-like devices powered by photons instead of electrons, says Scott Diddams, physicist and project leader at the National Institute of Standards and Technology and a coauthor on the study.

    “There are always tradeoffs between the highest performance, the smallest size, and the best ease of integration. But even in this first demonstration, these optical oscillators have many advantages; they are on par with, and in some cases even better than, what is available with widespread electronic technology,” Vahala says.

    The new technique is described in a paper that will be published in the journal Science on July 18. Other authors on this paper include Hansuek Lee, who is a visiting associate at Caltech. The work was sponsored by the DARPA’s ORCHID and PULSE programs; the Caltech Institute for Quantum Information and Matter (IQIM), an NSF Physics Frontiers Center with support of the Gordon and Betty Moore Foundation; and the Caltech Kavli NanoScience Institute.

    See the full article here.

    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”
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  • richardmitnick 9:13 am on June 11, 2014 Permalink | Reply
    Tags: , , , Fiber technology, , Laser Technology, ,   

    From CERN: “Laser acceleration, now with added fibre” 

    CERN New Masthead
    CERN

    8 Jan 2013 [Where has this been?]
    Cian O’Luanaigh

    The International Coherent Amplification Network (ICAN) is studying the potential of lasers for collision physics. CERN is a beneficiary of the project and will collaborate with 15 other institutes from around the world, including KEK in Japan, Fermilab in the USA, and DESY in Germany. “The network is looking into existing fibre laser technology, which we believe has fantastic potential for accelerators,” says Gerard Mourou, ICAN co-ordinator at the École Polytechnique in France. “The hope is to make laser acceleration competitive with traditional radio-frequency acceleration techniques.”

    fiber

    Laser acceleration is currently limited by the “single-shot” nature of the technology. As there is no way to remove the excess heat created by lasers, they cannot be sustained for high-energy acceleration. However, using fibre lasers may resolve this issue. By using laser diodes to pump the laser through typical optical fibres, fibre lasers absorb the heat created, thus giving fibre lasers very high repetition rates. This, in turn, may allow the laser to be sustained long enough to accelerate particles into collisions. Fibres should also improve the overall power efficiency of lasers by 35-40%, making them more economically feasible for experiments. “ICAN is studying whether we can turn the potential of fibre lasers into feasible technology,” says Gerard. “Once we have achieved this, we can then look at direct laser applications for accelerators.”

    “CERN accelerator experts will advise collaborating institutions to define the requirements useful for collision physics,” says Jean-Pierre Koutchouk, CERN advisor for international relations in accelerators and technology. “CERN’s contribution to the ICAN project is part of a wider strategy to encourage the development of laser acceleration technologies. By supporting ICAN and similar research projects, CERN will be contributing to the R&D of potentially ground-breaking accelerator technologies.”

    ICAN is only the beginning and, if all goes as expected, we will be seeing more accelerator projects based on fibre lasers. “We’re considering ICAN as an 18-month-long preparatory phase, vetting the laser technology for a possible longer project based on ICAN laser concepts,” concludes Gerard.

    The ICAN kick-off meeting was held at CERN on 22 February 2012. The network has received half a million euros in the framework of the FP7 Capacities programme.

    See the full article here.

    Meet CERN in a variety of places:

    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New
    ALICE
    CERN ALICE New

    CMS
    CERN CMS New

    LHCb
    CERN LHCb New

    LHC

    CERN LHC New

    LHC particles

    Quantum Diaries


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  • richardmitnick 1:57 pm on May 28, 2014 Permalink | Reply
    Tags: , Laser Technology, , ,   

    From Berkeley Lab: “A Path Toward More Powerful Tabletop Accelerators” 

    Berkeley Logo

    Berkeley Lab

    May 28, 2014
    Kate Greene kgreene@lbl.gov

    Making a tabletop particle accelerator just got easier. A new study shows that certain requirements for the lasers used in an emerging type of small-area particle accelerator can be significantly relaxed. Researchers hope the finding could bring about a new era of accelerators that would need just a few meters to bring particles to great speeds, rather than the many kilometers required of traditional accelerators. The research, from scientists at the U.S. Department of Energy’s (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab), is presented as the cover story in the May special issue of Physics of Plasmas.

    Traditional accelerators, like the Large Hadron Collider where the Higgs boson was recently discovered, rely on high-power radio-frequency waves to energize electrons. The new type of accelerator, known as a laser-plasma accelerator, uses pulses of laser light that blast through a soup of charged particles known as a plasma; the resulting plasma motion, which resemble waves in water, accelerates electrons riding atop the waves to high speeds.

    http://newscenter.lbl.gov/wp-content/uploads/figure_wake_02_wArrow_wLabels.png
    3D Map of the longitudinal wakefield generated by the incoherent combination of 208 low-energy laser beamlets. In the region behind the driver, the wakefield is regular. Credit: Carlo Benedetti, Berkeley Lab

    The problem, however, is creating a laser pulse that’s powerful enough to compete with the big accelerators. In particular, lasers need to have the capability to fire a high-energy pulse thousands of times a second. Today’s lasers can only manage one pulse per second at the needed energy levels.

    “If you want to make a device that’s of use for particle physics, of use for medical applications, of use for light source applications, you need repetition rate,” explains Wim Leemans, physicist at Berkeley Lab. In January of 2013, the DOE held a workshop on laser technology for accelerators. At the time, says Leemans, the big question was how to get from the current technology to the scaled up version.

    Conventional wisdom holds that many smaller lasers, combined in a particular way, could essentially create one ultra powerful pulse. In theory, this sounds fine, but the practical requirements to build such a system have seemed daunting. For instance, it was believed that the light from the smaller lasers would need to be precisely matched in color, phase, and other properties in order to produce the electron-accelerating motion within the plasma. “We thought this was really challenging,” says Leemans, “We thought, you need this nice laser pulse, and everything needs to be done properly to control the laser pulse.”

    But the new Berkeley Lab study has found this isn’t the case. Paper co-authors Carlo Benedetti, Carl Schroeder, Eric Esarey and Leemans wanted to see what an erratic laser pulse would actually do inside a plasma. Guided by theory and using computer simulations to test various scenarios, the researchers looked at how beams of various colors and phases—basically a hodgepodge of laser light—affected the plasma. They soon discovered, no matter the beam, the plasma didn’t care.

    “The plasma is a medium that responds to a laser, but it doesn’t respond immediately,” says Benedetti, a physicist at Berkeley Lab. The light is just operating on a faster time scale and a smaller length scale, he explains. All of the various interference patterns and various electromagnetic fields average out in the slow-responding plasma medium. In other words, once laser light gets inside the plasma, many of the problems disappear.

    “As an experimentalist for all these years we’re trying to make these perfect laser pulses, and maybe we didn’t need to worry so much,” says Leemans. “I think this will have a big impact on the laser community and laser builders because all of a sudden, they’ll think of approaches where before hand all of us said, ‘No, no, no. You can’t do that.’ This new result says, well maybe you don’t have to be all that careful.”

    Leemans says the ball is back in the experimentalists’ and laser builders’ court to prove that the idea can work. In 2006, he and his team demonstrated a three-centimeter long plasma accelerator. Where a traditional accelerator can take kilometers to drive an electron to 50 giga-electron volts (GeV), Leemans and team showed that a mini-laser plasma accelerator could get electrons to 1 GeV in just three centimeters with a laser pulse of about 40 terawatt. To go to higher electron energies, in 2012, a larger more powerful laser was installed at the Berkeley Lab Laser Accelerator (BELLA) facility with a petawatt pulse (1 quadrillion watts) that lasts 40 femtoseconds, which is now being used in experiments that aim at generating a 10 GeV beam.

    Still, the goal of a high-repetition rate, 10-GeV laser-plasma accelerator that fires a thousand pulses or more per second, is at least five to ten years away, says Leemans. But a new project called k-BELLA (k is for kilohertz) is in the works that will use the principles of combined, messy laser light sources to produce fast, more powerful laser pulses. “Once we synthesize a pulse at higher repetition rates,” says Leemans, “we will be on our way towards a kilohertz GeV laser plasma accelerator.”

    This work was supported by the DOE Office of Science and used the facilities of the National Energy Research Scientific Computing Center (NERSC) located at Berkeley Lab.

    1. # #

    See the full article here.

    A U.S. Department of Energy National Laboratory Operated by the University of California

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  • richardmitnick 10:10 pm on April 16, 2014 Permalink | Reply
    Tags: , Laser Technology, , ,   

    From SLAC Lab: “Scientists Capture Ultrafast Snapshots of Light-driven Superconductivity” 

    April 16, 2014
    No Writer Credit

    A new study pins down a major factor behind the appearance of superconductivity – the ability to conduct electricity with 100 percent efficiency – in a promising copper-oxide material.

    Scientists used carefully timed pairs of laser pulses at SLAC National Accelerator Laboratory’s Linac Coherent Light Source (LCLS) to trigger superconductivity in the material and immediately take X-ray snapshots of its atomic and electronic behavior as superconductivity emerged.

    und
    The Undulator Hall at SLAC’s Linac Coherent Light Source X-ray laser. (Brad Plummer/SLAC)

    They discovered that so-called “charge stripes” of increased electrical charge melted away as superconductivity appeared. Further, the results help rule out the theory that shifts in the material’s atomic lattice hinder the onset of superconductivity.

    Armed with this new understanding, scientists may be able to develop new techniques to eliminate these charge stripes and help pave the way for room-temperature superconductivity, often considered the holy grail of condensed matter physics. The demonstrated ability to rapidly switch between the insulating and superconducting states could also prove useful in advanced electronics and computation.

    The results, from a collaboration led by scientists from the Max Planck Institute for the Structure and Dynamics of Matter in Germany and the U.S. Department of Energy’s SLAC and Brookhaven national laboratories, were published online April 16, 2014, in the journal Physical Review Letters.

    “The very short timescales and the need for high spatial resolution made this experiment extraordinarily challenging,” said co-author Michael Först, a scientist at the Max Planck Institute. “Now, using femtosecond X-ray pulses, we found a way to capture the quadrillionths-of-a-second dynamics of the charges and the crystal lattice. We’ve broken new ground in understanding light-induced superconductivity.”

    Josh Turner, an LCLS staff scientist, said, “This represents a very important result in the field of superconductivity using LCLS. It demonstrates how we can unravel different types of complex mechanisms in superconductivity that have, up until now, been inseparable.”

    He added, “To make this measurement, we had to push the limits of our current capabilities. We had to measure a very weak, barely detectable signal with state-of-the-art detectors, and we had to tune the number of X-rays in each laser pulse to see the signal from the stripes without destroying the sample.”

    Ripples in Quantum Sand

    The compound used in this study was a layered material consisting of lanthanum, barium, copper, and oxygen grown at Brookhaven Lab by physicist Genda Gu. Each copper oxide layer contained the crucial charge stripes.

    man
    Physicist Genda Gu in the Brookhaven Lab facility where the copper-oxide materials were grown for this study.

    “Imagine these stripes as ripples frozen in the sand,” said John Hill, a Brookhaven Lab physicist and coauthor on the study. “Each layer has all the ripples going in one direction, but in the neighboring layers they run crosswise. From above, this looks like strings in a pile of tennis racquets. We believe that this pattern prevents each layer from talking to the next, thus frustrating superconductivity.”

    To excite the material and push it into the superconducting phase, the scientists used mid-infrared laser pulses to “melt” those frozen ripples. These pulses had previously been shown to induce superconductivity in a related compound at a frigid 10 Kelvin (minus 442 degrees Fahrenheit).

    “The charge stripes disappeared immediately,” Hill said. “But specific distortions in the crystal lattice, which had been thought to stabilize these stripes, lingered much longer. This shows that only the charge stripes inhibit superconductivity.”

    Stroboscopic Snapshots

    To capture these stripes in action, the collaboration turned to SLAC’s LCLS X-ray laser, which works like a camera with a shutter speed faster than 100 femtoseconds, or quadrillionths of a second, and provides atomic-scale image resolution. LCLS uses a section of SLAC’s 2-mile-long linear accelerator to generate the electrons that give off X-ray light.

    Researchers used the so-called “pump-probe” approach: an optical laser pulse strikes and excites (pumps) the lattice and an ultrabright X-ray laser pulse is carefully synchronized to follow within femtoseconds and measure (probe) the lattice and stripe configurations. Each round of tests results in some 20,000 X-ray snapshots of the changing lattice and charge stripes, a bit like a strobe light rapidly illuminating the process.

    To measure the changes with high spatial resolution, the team used a technique called resonant soft X-ray diffraction. The LCLS X-rays strike and scatter off the crystal into the detector, carrying time-stamped signatures of the material’s charge and lattice structure that the physicists then used to reconstruct the rise and fall of superconducting conditions.

    “By carefully choosing a very particular X-ray energy, we are able to emphasize the scattering from the charge stripes,” said Brookhaven Lab physicist Stuart Wilkins, another co-author on the study. “This allows us to single out a very weak signal from the background.”

    Toward Superior Superconductors

    The X-ray scattering measurements revealed that the lattice distortion persists for more than 10 picoseconds (trillionths of a second) – long after the charge stripes melted and superconductivity appeared, which happened in less than 400 femtoseconds. Slight as it may sound, those extra trillionths of a second make a huge difference.

    “The findings suggest that the relatively weak and long-lasting lattice shifts do not play an essential role in the presence of superconductivity,” Hill said. “We can now narrow our focus on the stripes to further pin down the underlying mechanism and potentially engineer superior materials.”

    Andrea Cavalleri, director of the Max Planck Institute, said, “Light-induced superconductivity was only recently discovered, and we’re already seeing fascinating implications for understanding it and going to higher temperatures. In fact, we have observed the signature of light-induced superconductivity in materials all the way up to 300 Kelvin (80 degrees Fahrenheit) – that’s really a significant breakthrough that warrants much deeper investigations.”

    Other collaborators on this research include the University of Groningen, the University of Oxford, Diamond Light Source, the Lawrence Berkeley National Laboratory, Stanford University, the European XFEL, the University of Hamburg and the Center for Free-Electron Laser Science.

    The research conducted at the Soft X-ray Materials Science (SXR) experimental station at SLAC’s LCLS – a DOE Office of Science user facility – was funded by Stanford University, Lawrence Berkeley National Laboratory, the University of Hamburg and the Center for Free-Electron Laser Science (CFEL). Work performed at Brookhaven Lab was supported by the DOE’s Office of Science.

    See the full article here.

    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.
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