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  • richardmitnick 9:42 pm on October 14, 2015 Permalink | Reply
    Tags: , , , Laser Technology   

    From ESA: “AIMing a light across millions of kilometres” 

    European Space Agency

    13 October 2015

    Laser communication with Earth

    Imagine beaming a light across millions of kilometres of empty space, all the way back to Earth. ESA’s proposed Asteroid Impact Mission [AIM] is intended to do just that: demonstrate laser communications across an unprecedented void.

    ESA AIM Asteroid Impact Mission

    The Asteroid Impact Mission, or AIM, undergoing detailed design ahead of a final go/no-go decision by ESA’s Ministerial Council in December 2016, is a deep-space technology-demonstration mission that would also be humanity’s first probe to a double asteroid.

    Among its innovative technologies, laser communications would return results to scientists several times faster than standard radio signals.

    “Optical communications in general is not yet a well-established technology for space and ESA’s European Data Relay System (EDRS) will be the first commercial application,” explains ESA optics engineer Zoran Sodnik.

    ESA’s laser station

    “In principle it works something like Morse code, with encoded rapid flashes on and off. ERDS with satellites in high orbits will use laser links to return environmental data from Europe’s low-orbiting Sentinel satellites on a realtime basis, a technique previously demonstrated using ESA’s Alphasat and Artemis telecom missions.

    “In 2013 ESA’s Optical Ground Station in Tenerife participated in a two-way contact with NASA’s LADEE lunar orbiter, across 400 000 km.

    “But AIM will need to operate much further: we are benchmarking a maximum span of 75 million kilometres, or half the distance between Earth and the Sun. That might sound like a lot, but operating around Mars one day will involve much further distances still.”

    Transmitter telescope

    A laser beam shone back from AIM’s 13.5 cm-diameter laser telescope at such a distance would have a ground footprint of about 1100 km – further than from London to Berlin. Also a lot but the equivalent radio beam radiating out across space would end up wider than our whole planet.

    “The much higher frequency of laser light is what gives us higher directivity and as a result increased bandwidth,” adds ESA laser engineer Clemens Heese.

    “At the same time, many photons will get lost on the way, so we need to use sophisticated photon counting methods to detect the signal reliably using our receiver telescope of around 1 m diameter.

    AIM laser

    While radio communications is a very mature technology and close to optimum efficiency, there’s still lots of room for development with optical communications. So this is the way we need to go to really boost the quantity and speed of data we can deliver to scientists.”

    To meet the challenge, ESA’s AIM team this month issued technology pre-development contracts to industry to tackle key issues including telescope design, detector electronics and coarse and fine-pointing systems. To give an idea of the kind of pointing required, AIM will need to align with the signal from Earth to within the diameter of planet Mars seen in our terrestrial sky.

    Laser for altimetry

    “At 39.3 kg, AIM’s laser system will be one of the single largest payload items,” explains Andres Galvez, heading ESA’s Science Analysis and System Support Unit.

    “We intend to gain maximum utility from it, by also using it for scientific purposes: the laser can also serve as an altimeter to chart the asteroid.”

    The system design is led by RUAG Space in Switzerland, building on its existing family of Optel laser communication terminals, the latest of which is tailored for direct-to-Earth downlinks from minisatellites.

    See the full article here .

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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 2:53 pm on October 9, 2015 Permalink | Reply
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    From EPFL: “Using optical fibre to generate a two-micron laser” 

    EPFL bloc

    Ecole Polytechnique Federale Lausanne

    Emmanuel Barraud

    Camille Brès and Svyatoslav Kharitonov of EPFL

    Lasers with a wavelength of two microns could move the boundaries of surgery and molecule detection. Researchers at EPFL have managed to generate such lasers using a simple and inexpensive method.

    In recent years, two-micron lasers (0.002 millimetre) have been of growing interest among researchers. In the areas of surgery and molecule detection, for example, they offer significant advantages compared to traditional, shorter-wavelength lasers.
    However, two-micron lasers are still in their infancy and not yet as mature as their telecom counterparts (1.55-micron). Moreover sources currently used in labs are typically bulky and expensive. Optical fibre-based 2 micron lasers are an elegant solution to these issues. This is where researchers at Photonics Systems Laboratory (PHOSL) come in.

    In an article published in Light: Science & Applications, the team of Camille Brès at EPFL described a way to design these lasers at a lower cost, by changing the way optical fibres are connected to each other. Thanks to the new configuration, they were able not only to produce very good 2 micron lasers, but also to do without an expensive and complex component that is normally required.

    Bloodless surgery and long-range molecule détection

    Two-micron spectral domain has potential applications in medicine, environmental sciences and industry. At these wavelengths, the laser light is easily absorbed by water molecules, which are the main constituents of human tissue. In the realm of high precision surgery, they can be used to target water molecules during an operation and make incisions in very small areas of tissue without penetrating deeply. What is more, the energy from the laser causes the blood to coagulate on the wound, which prevents bleeding.

    Two-micron lasers are also very useful for detecting key meteorological data over long distances through the air. Not to mention that they are highly effective in the processing of various industrial materials.

    Replacing a cop with a detour

    To create a 2 micron fibre-laser, light is usually injected into an optical-fibre ring containing a gain region which amplifies 2 micron light. The light circulates in the ring, passing through the gain region many times thus gaining more and more power, until becoming a laser. For optimal operation, these systems include a costly component called isolator, which forces the light to circulate in a single direction.

    At PHOSL, researchers built a thulium-doped fibre laser that works without an isolator. Their idea was to connect the fibres differently, to steer light instead of stopping it. “We plug a kind of deviation that redirects the light heading in the wrong direction, putting it back on track”, said Camille Brès. This means no more need for the isolator, whose job is to stop light moving in the wrong direction, sort of like a traffic cop. “We replaced the traffic cop with a detour,” said Svyatoslav Kharitonov, the article’s lead author.

    Higher quality laser

    The new system not only proved to be less expensive than more traditional ones, it also showed it could generate a higher quality laser light. The explanation is as follows: the laser output gets purified because light interacts with itself in a very special way, thanks to the amplifying fibre’s composition and dimensions, and the high power circulating in this atypical laser architecture.
    “While the association of amplifying fibres and high power usually weakens traditional lasers performance, it actually improves the quality of this laser, thanks to our specific architecture”, said Svyatoslav Kharitonov.

    See the full article here .

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    EPFL is Europe’s most cosmopolitan technical university. It receives students, professors and staff from over 120 nationalities. With both a Swiss and international calling, it is therefore guided by a constant wish to open up; its missions of teaching, research and partnership impact various circles: universities and engineering schools, developing and emerging countries, secondary schools and gymnasiums, industry and economy, political circles and the general public.

  • richardmitnick 7:25 pm on August 18, 2015 Permalink | Reply
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    From LLNL: “National Ignition Facility fires 300th shot in FY15” 

    Lawrence Livermore National Laboratory

    NIF Bloc

    Aug. 18, 2015
    Breanna Bishop

    NIF’s target chamber is where the magic happens – temperatures of 100 million degrees and pressures extreme enough to compress the target to densities up to 100 times the density of lead are created there. Photo by Damien Jemison/LLNL

    Last week, the National Ignition Facility (NIF) fired its 300th laser target shot in fiscal year (FY) 2015, meeting the year’s goal more than six weeks early. In comparison, the facility completed 191 target shots in FY 2014. Located at Lawrence Livermore National Laboratory (LLNL), the NIF is the world’s most energetic laser.

    Increasing the shot rate has been a top priority for the Inertial Confinement Fusion (ICF) Program and in particular the NIF team at LLNL. The greater than 50 percent increase in NIF shots from FY 2014 to FY 2015 is a direct result of the implementation of an efficiency study conducted in FY 2014 for the NIF.

    NIF is funded by the National Nuclear Security Administration (NNSA), the agency charged with ensuring the nation’s nuclear security. The chief mission of NIF is to provide experimental insight and data for NNSA’s science-based Stockpile Stewardship Program in the area of high-energy-density physics, a scientific field of direct relevance to nuclear deterrence and national nuclear security.

    “Demand for experiments at NIF have always exceeded capacity. The impressive work by the team at NIF to produce additional shots has provided important new opportunities for NIF users and increased this unique scientific platform’s contributions to national security,” said Brig. Gen Stephen Davis, USAF, acting deputy administrator for Defense Programs. “I congratulate the NIF team and its many partners for not only meeting, but exceeding the goal.”

    The NIF Control Room preparing for the 300th shot. From left: Shot Director Dean Latray, Operations Manager Bruno Van Wonterghem and Lead Operator Rod Rinnert. Photo by Jason Laurea/LLNL.

    “Achieving 300 shots this year enabled so many critical accomplishments: first-of-a-kind dynamic materials data, more efficiently driven ICF capsules, increased opportunities for academic users, new radiation sources for the Department of Defense and acceleration of new diagnostic development,” said Keith LeChien, director of ICF for NNSA.

    “This is a remarkable achievement for team NIF, whose incredible effort and persistence turned this huge challenge into a reality,” said LLNL Director Bill Goldstein. “Without the support of NNSA and our many partners, this would not have been possible.”

    This 120-day efficiency study was developed in partnership with other NNSA laboratories and drew on best practices at the Z Facility at Sandia National Laboratories and the Omega Laser at the University of Rochester. This study identified more than 80 improvements to equipment and procedures that could lead to reduced time and effort for fielding experiments.

    To date, the NIF team has implemented more than 50 of these improvements and will continue implementing the remainder of the improvements in FY 2016. Improvements include equipment modifications to reduce the time needed to perform critical tasks. Some of the most significant were control system improvements to streamline the shot cycle; process improvements to reduce time needed to align targets and diagnostics; and user interface improvements to make it easier for users to set up and execute experiments.

    See the full article here.

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    Operated by Lawrence Livermore National Security, LLC, for the Department of Energy’s National Nuclear Security
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  • richardmitnick 1:57 pm on August 14, 2015 Permalink | Reply
    Tags: Laser Technology, Max Planck Institute of Quantum Optics   

    From MPG: “A novel source of X-rays for imaging purposes” 

    Max Planck Institute of Quantum Optics bloc

    Max Planck Institute of Quantum Optice

    June 16, 2015
    Thorsten Naeser

    Physicists at LMU Munich and the Max Planck Institute of Quantum Optics have validated a novel laser-driven means of generating bright and highly energetic X-ray beams. The method opens up new ways of imaging the fine structure of matter.

    For over a century, medical imaging has made use of X-rays produced in a specialized type of vacuum tube. The major disadvantage of this method lies in the poor quality of the emitted radiation. The source emits radiation from a large spot into all directions and over a broad energy range. These features are responsible for the relatively modest resolution attainable with this mode of imaging. X-rays generated in synchrotrons provide much higher resolution, but their dimensions and cost preclude their routine use in clinical settings. However, an alternative approach is now available, for two laser pulses can generate X-rays of similar quality to synchrotron radiation in devices with a far smaller footprint: One pulse accelerates electrons to very high energy and the other forces them into an undulating motion. Under these conditions, electrons emit X-radiation that is both highly energetic (‚hard‘) and highly intense, and is therefore ideal for probing the microscopic structure of matter. Now, physicists based at the Laboratory for Attosecond Physics (LAP) at LMU Munich and the Max Planck Institute of Quantum Optics (MPQ) have developed such a laser-driven X-ray source for the first time. With the aid of two laser pulses, the researchers have generated ultrashort bursts of X-rays with defined wavelengths tailored for different applications. The new source can image structures of varying composition with a resolution of less than 10 micrometers. This breakthrough opens up a range of promising perspectives in materials science, biology and – in particular – medicine.

    The ATLAS Lasersystem based in the Laboratory for Extreme Photonics of the Ludwig-Maximilians University Munich, serves as a light source for the new brilliant X-ray radiation. (Photo: Thorsten Naeser)

    Imaging of microscopic structures in any sample of matter requires the use of a very brilliant beam of light with a very short wavelength. Brilliant radiation is able to concentrate a maximum amount of light quanta or photons of a single defined wavelength within the smallest area and shortest duration. Hard X-radiation is therefore ideal for this purpose, because it penetrates matter and exhibits wavelengths of a few hundredths of a nanometer (few-hundredths of a billionth of a meter, 10-11 m). Unfortunately, the only sources of high-intensity beams of hard X-rays so far available are particle accelerators, which are typically huge and highly expensive. But there is, in principle, a far more economical and compact way of doing the job – with optical light.

    A team at the Laboratory for Attosecond Physics, which is run jointly by LMU and the MPQ, has now taken an important step towards realizing this goal. Led by Prof. Stefan Karsch and Dr. Laszlo Veisz, the scientists have succeeded in generating bright beams of hard X-radiation by purely optical means. Moreover, the wavelength of the emitted radiation can be readily adjusted to cater for different applications.

    The physicists focused a laser pulse, lasting 25 femtoseconds and packing 60 terawatts (6×10^13 Watts) of power, onto a fine jet of hydrogen gas. Note here that the output of a nuclear power station – 1500 MW (1.5×109 Watts) – is very modest by comparison, but each pulse only lasts for 25 millionths of a billionth of a second. The strong electric field associated with each pulse knocks negatively charged electrons out of the gas, giving rise to a cloud of ionized particles, or ‘plasma’. The wavefront courses through the plasma like a snow-plow, sweeping the electrons aside and leaving behind the positively charged atoms (which are much heavier). The separation of oppositely charged particles generates very strong electrical fields, which cause the displaced electrons to whiplash back and forth. This in turn creates a wave-like pattern within the plasma, which propagates in the wake of the laser pulse, rather like the trailing wave caused by the keel of a speedboat racing on a lake. A fraction of the free electrons are caught up in this wave and can effectively ride on it like a surfer, directly behind the advancing laser pulse. Indeed, in this ‘wakefield’, the surfing electrons can be rapidly accelerated to velocities very near the speed of light.

    When the electrons have reached their maximal speed they are allowed to collide head-on with a counter-propagating laser pulse, creating a so-called optical undulator whose oscillating electric field causes the free electrons to oscillate along a direction perpendicular to their direction of propagation. Highly energetic electrons that are forced to oscillate in this way emit radiation in the form of X-ray photons with wavelengths as short as 0.03 nm. In addition, in these experiments, the higher harmonics (waves whose frequency is an integer multiple of the fundamental frequency) entrained on the electron motions by the light field could be detected directly in the X-ray spectrum – a feat that has been attempted many times on conventional particle accelerators without success.

    One of the great advantages of the new system in comparison with conventional X-ray sources is that the wavelength of the emitted light can be tuned over a wide range. This ability to alter the wavelength allows radiologists to analyze different types of tissue, for instance. By fine-tuning the incident beam, one can gain the maximum information about the sample one wishes to characterize.

    Not only is the laser-driven radiation tunable and extremely bright, it is produced in pulsed form. Each 25-fs laser pulse gives rise to X-ray flashes of a few fs duration. This makes it useful for applications such as time-resolved spectroscopy, which is used to investigate ultrafast processes at the level of atoms and electrons. The intensity of the pulses (i.e. the number of photons per pulse) generated by the new source is not yet high enough for this task, but the researchers hope to overcome this obstacle with the aid of the facilities at the new Centre for Advanced Laser Applications (CALA), now being built on the Garching Campus.

    The new optically generated radiation can also be combined with phase-contrast X-ray tomography, an imaging procedure that is being refined by Prof. Franz Pfeiffer of the Technical University of Munich (TUM). This technique extracts information from the light that is scattered (rather than that absorbed) by an object. “Using this method, we can already image structures as small as 10 micrometers in diameter in opaque materials,” Stefan Karsch explains. “With our new X-ray source, we will be able to obtain even more detailed information from living tissues and other materials,” he adds.

    See the full article here.

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    Max Planck Institute of Quantum Optics campus

    Research at the Max Planck Institute of Quantum Optics
    Light can behave as an electromagnetic wave or a shower of particles that have no mass, called photons, depending on the conditions under which it is studied or used. Matter, on the other hand, is composed of particles, but it can actually exhibit wave-like properties, giving rise to many astonishing phenomena in the microcosm.

    At our institute we explore the interaction of light and quantum systems, exploiting the two extreme regimes of the wave-particle duality of light and matter. On the one hand we handle light at the single photon level where wave-interference phenomena differ from those of intense light beams. On the other hand, when cooling ensembles of massive particles down to extremely low temperatures we suddenly observe phenomena that go back to their wave-like nature. Furthermore, when dealing with ultrashort and highly intense light pulses comprising trillions of photons we can completely neglect the particle properties of light. We take advantage of the large force that the rapidly oscillating electromagnetic field exerts on electrons to steer their motion within molecules or accelerate them to relativistic energies.

  • richardmitnick 9:30 am on August 11, 2015 Permalink | Reply
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    From LLNL: “Researchers reveal new electron ring formations” 

    Lawrence Livermore National Laboratory

    Aug. 11, 2015
    Breanna Bishop
    bishop33@llnl.gov (link sends e-mail)

    Using the ultra-short-pulse Callisto laser system at LLNL’s Jupiter Laser Facility, a team of scientists from LLNL and UCLA revealed new, never-before-seen electron ring formations. Photo by Julie Russell/LLNL

    This image from the 3D simulation shows the laser pulse propagating to the right through the low-density plasma. The black region behind the laser contains background ions, which are responsible for accelerating electrons in this region to high energy. The white contours represent regions of high background electron density; the roughly triangular region they form between the two black regions is called the “pocket,” and it is able to guide electrons through the plasma and allow them to leave it with a ring-like structure.

    Laser wakefield acceleration, a process where electron acceleration is driven by high-powered lasers, is well-known for being able to produce high-energy beams of electrons in tabletop-scale distances. However, in recent experiments, a team of scientists from Lawrence Livermore National Laboratory (LLNL) and the University of California, Los Angeles (UCLA) revealed new, never-before-seen electron ring formations in addition to the typically observed beams.

    In a recently published Physical Review Letters , the team described electron acceleration experiments performed at LLNL’s Jupiter Laser Facility. Using the ultra-short-pulse Callisto laser system, a plasma was produced in a low-density gas cell target. The interaction of the high-intensity laser with the gas created a relativistic plasma wave, which then accelerated some of the electrons in the plasma to more than 100 megaelectron volt (MeV) energies.

    These electron beams are usually directed along the laser axis and have fairly low divergence. In these experiments, the typical beams were observed, but in certain cases were also accompanied by a second, off-axis beam that had a ring-like shape. This new feature had never before been reported, and its origin was unclear until the UCLA collaborators finished computationally intensive three-dimensional calculations of the experimental conditions.

    “The dynamics of the plasma wave are often calculated in simulations, but the small spatial scale and fast timescale of the wakefield process has made direct measurements of many effects difficult or impractical,” said lead author Brad Pollock. “The discovery of new features, such as the electron rings here, allows us to compare with simulations and infer what is going on in the experiments with much greater confidence.”

    In the simulations, a ring-like electron structure was produced during the wakefield acceleration process if the plasma was sufficiently long and the total number of electrons was large enough to perturb the plasma wave structure. Under these conditions, the plasma wave structure was modified in such a way as to force some electrons off of the laser axis and into a “pocket” outside of the plasma wave, which then guided some of these electrons through the remainder of the plasma.

    “In addition to the diagnostic implications of this particular feature, it may also be possible to tailor the parameters of electron ring-beams for their own applications, including accelerating positively charged particles – positrons, for example,” Pollock added.

    LLNL co-authors include Felicie Albert, Arthur Pak and Joseph Ralph, and UCLA co-authors include Frank Tsung, Jessica Shaw, Chris Clayton, Asher Davidson, Nuno Lemos, Ken Marsh, Warren Mori and Chan Joshi.

    See the full article here.

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    Operated by Lawrence Livermore National Security, LLC, for the Department of Energy’s National Nuclear Security
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  • richardmitnick 9:32 am on August 3, 2015 Permalink | Reply
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    From ASU: “ASU researchers demonstrate the world’s first white lasers” 

    ASU Bloc


    July 28, 2015

    Sharon Keeler, sharon.keeler@asu.edu
    Ira A. Fulton Schools of Engineering

    This schematic illustrates the novel nanosheet with three parallel segments created by the researchers, each supporting laser action in one of three elementary colors. The device is capable of lasing in any visible color, completely tunable from red, green to blue, or any color in between. When the total field is collected, a white color emerges.
    Photo by: ASU/Nature Nanotechnology

    More luminous and energy efficient than LEDs, white lasers look to be the future in lighting and light-based wireless communication

    While lasers were invented in 1960 and are commonly used in many applications, one characteristic of the technology has proven unattainable. No one has been able to create a laser that beams white light.

    Researchers at Arizona State University have solved the puzzle. They have proven that semiconductor lasers are capable of emitting over the full visible color spectrum, which is necessary to produce a white laser.

    The researchers have created a novel nanosheet – a thin layer of semiconductor that measures roughly one-fifth of the thickness of human hair in size with a thickness that is roughly one-thousandth of the thickness of human hair – with three parallel segments, each supporting laser action in one of three elementary colors. The device is capable of lasing in any visible color, completely tunable from red, green to blue, or any color in between. When the total field is collected, a white color emerges.

    The researchers, engineers in ASU’s Ira A. Fulton Schools of Engineering, published their findings in the July 27 advance online publication of the journal Nature Nanotechnology. Cun-Zheng Ning, professor in the School of Electrical, Computer and Energy Engineering, authored the paper, A monolithic white laser, with his doctoral students Fan Fan, Sunay Turkdogan, Zhicheng Liu and David Shelhammer. Turkdogan and Liu completed their doctorates after this research.

    The technological advance puts lasers one step closer to being a mainstream light source and potential replacement or alternative to light emitting diodes (LEDs). Lasers are brighter, more energy efficient, and can potentially provide more accurate and vivid colors for displays like computer screens and televisions. Ning’s group has already shown that their structures could cover as much as 70 percent more colors than the current display industry standard.

    Another important application could be in the future of visible light communication in which the same room lighting systems could be used for both illumination and communication. The technology under development is called Li-Fi for light-based wireless communication, as opposed to the more prevailing Wi-Fi using radio waves. Li-Fi could be more than 10 times faster than current Wi-Fi, and white laser Li-Fi could be 10 to 100 times faster than LED based Li-Fi currently still under development.

    “The concept of white lasers first seems counterintuitive because the light from a typical laser contains exactly one color, a specific wavelength of the electromagnetic spectrum, rather than a broad-range of different wavelengths. White light is typically viewed as a complete mixture of all of the wavelengths of the visible spectrum,” said Ning, who also spent extended time at Tsinghua University in China during several years of the research.

    In typical LED-based lighting, a blue LED is coated with phosphor materials to convert a portion of the blue light to green, yellow and red light. This mixture of colored light will be perceived by humans as white light and can therefore be used for general illumination.

    Sandia National Labs in 2011 produced high-quality white light from four separate large lasers. The researchers showed that the human eye is as comfortable with white light generated by diode lasers as with that produced by LEDs, inspiring others to advance the technology.

    “While this pioneering proof-of-concept demonstration is impressive, those independent lasers cannot be used for room lighting or in displays,” Ning said. “A single tiny piece of semiconductor material emitting laser light in all colors or in white is desired.”

    Semiconductors, usually a solid chemical element or compound arranged into crystals, are widely used for computer chips or for light generation in telecommunication systems. They have interesting optical properties and are used to make lasers and LEDs because they can emit light of a specific color when a voltage is applied to them. The most preferred light emitting material for semiconductors is indium gallium nitride, though other materials such as cadmium sulfide and cadmium selenide also are used for emitting visible colors.

    The main challenge, the researchers noted, lies in the way light emitting semiconductor materials are grown and how they work to emit light of different colors. Typically a given semiconductor emits light of a single color – blue, green or red – that is determined by a unique atomic structure and energy bandgap.

    The “lattice constant” represents the distance between the atoms. To produce all possible wavelengths in the visible spectral range you need several semiconductors of very different lattice constants and energy bandgaps.

    “Our goal is to achieve a single semiconductor piece capable of laser operation in the three fundamental lasing colors. The piece should be small enough, so that people can perceive only one overall mixed color, instead of three individual colors,” said Fan. “But it was not easy.”

    “The key obstacle is an issue called lattice mismatch, or the lattice constant being too different for the various materials required,” Liu said. “We have not been able to grow different semiconductor crystals together in high enough quality, using traditional techniques, if their lattice constants are too different.”

    The most desired solution, according to Ning, would be to have a single semiconductor structure that emits all needed colors. He and his graduate students turned to nanotechnology to achieve their milestone.

    The key is that at nanometer scale larger mismatches can be better tolerated than in traditional growth techniques for bulk materials. High quality crystals can be grown even with large mismatch of different lattice constants.

    Recognizing this unique possibility early on, Ning’s group started pursuing the distinctive properties of nanomaterials, such as nanowires or nanosheets, more than 10 years ago. He and his students have been researching various nanomaterials to see how far they could push the limit of advantages of nanomaterials to explore the high crystal quality growth of very dissimilar materials.

    Six years ago, under U.S. Army Research Office funding, they demonstrated that one could indeed grow nanowire materials in a wide range of energy bandgaps so that color tunable lasing from red to green can be achieved on a single substrate of about one centimeter long. Later on they realized simultaneous laser operation in green and red from a single semiconductor nanosheet or nanowires. These achievements triggered Ning’s thought to push the envelope further to see if a single white laser is ever possible.

    Blue, necessary to produce white, proved to be a greater challenge with its wide energy bandgap and very different material properties.

    “We have struggled for almost two years to grow blue emitting materials in nanosheet form, which is required to demonstrate eventual white lasers, ” said Turkdogan, who is now assistant professor at University of Yalova in Turkey.

    After exhaustive research, the group finally came up with a strategy to create the required shape first, and then convert the materials into the right alloy contents to emit the blue color. Turkdogan said, “To the best of our knowledge, our unique growth strategy is the first demonstration of an interesting growth process called dual ion exchange process that enabled the needed structure.”

    This strategy of decoupling structural shapes and composition represents a major change of strategy and an important breakthrough that finally made it possible to grow a single piece of structure containing three segments of different semiconductors emitting all needed colors and the white lasers possible. Turkdogan said that, “this is not the case, typically, in the material growth where shapes and compositions are achieved simultaneously.”

    While this first proof of concept is important, significant obstacles remain to make such white lasers applicable for real-life lighting or display applications. One of crucial next steps is to achieve the similar white lasers under the drive of a battery. For the present demonstration, the researchers had to use a laser light to pump electrons to emit light. This experimental effort demonstrates the key first material requirement and will lay the groundwork for the eventual white lasers under electrical operation.

    See the full article here.

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    ASU is the largest public university by enrollment in the United States.[11] Founded in 1885 as the Territorial Normal School at Tempe, the school underwent a series of changes in name and curriculum. In 1945 it was placed under control of the Arizona Board of Regents and was renamed Arizona State College.[12][13][14] A 1958 statewide ballot measure gave the university its present name.
    ASU is classified as a research university with very high research activity (RU/VH) by the Carnegie Classification of Institutions of Higher Education, one of 78 U.S. public universities with that designation. Since 2005 ASU has been ranked among the Top 50 research universities, public and private, in the U.S. based on research output, innovation, development, research expenditures, number of awarded patents and awarded research grant proposals. The Center for Measuring University Performance currently ranks ASU 31st among top U.S. public research universities.[15]

    ASU awards bachelor’s, master’s and doctoral degrees in 16 colleges and schools on five locations: the original Tempe campus, the West campus in northwest Phoenix, the Polytechnic campus in eastern Mesa, the Downtown Phoenix campus and the Colleges at Lake Havasu City. ASU’s “Online campus” offers 41 undergraduate degrees, 37 graduate degrees and 14 graduate or undergraduate certificates, earning ASU a Top 10 rating for Best Online Programs.[16] ASU also offers international academic program partnerships in Mexico, Europe and China. ASU is accredited as a single institution by The Higher Learning Commission.

    ASU Tempe Campus
    ASU Tempe Campus

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    About Phys.org in 100 Words

    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 11:06 am on July 29, 2015 Permalink | Reply
    Tags: , Laser Technology,   

    From phys.org: “Japanese team fires world’s most powerful laser” 


    July 29, 2015
    Bob Yirka

    GEKKO XII — at the Osaka University’s Institute for Laser Engineering. Credit: KASUGA, Sho

    A team of researchers and engineers at Japan’s Osaka University is reporting that they have successfully fired what they are claiming is the world’s most powerful laser. In their paper published in the journal Plasma Physics and Controlled Fusion in 2012, the team described their laser and how it works.

    The team now reports that they fired the laser (called the Laser for Fast Ignition Experiments [LFEX]) for a very short period of time—a pulse of just a trillionth of a second. But that pulse was a doozy, emitting 2-petawatts of power, or put another way 2 quadrillion watts.

    Lasers have come a long way since their humble beginnings in the early 60’s, but still work much the same way—light is amplified via a gain medium through pumping and the result is light that is emitted coherently, which allows it to be narrowly focused. This new laser is approximately 300 feet long, taking up most of a large room, but interestingly, because the pulse is of such short duration, it does not need much energy to create the beam, just a few Joules, or as they team notes, not much more than it would take to run a microwave oven for a few seconds—special glass lamps were used to boost the energy of the beam as it passed through. The research team claims also that not only does the laser generate approximately twice as much power as a similar rival laser at the University of Texas, but has approximately 100 times as much energy.

    The team reports also that their configuration is only the beginning, they plan to create stronger and stronger lasers with a goal of achieving 10 petawatts. Such lasers, at least for now, are mostly only of scientific interest, to sustain a pulse long enough to be of practical use would require more power than would likely be available, at least for now. A 2 petawatt laser for example, would require more energy to run continuously, than is currently produced by the whole world, thus giant lasers used as weapons to take down aircraft, drones or missiles (or the Death Star) at great distances are not likely to happen any time soon.

    See the full article here.

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    About Phys.org in 100 Words

    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 2:00 pm on July 21, 2015 Permalink | Reply
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    From European XFEL: “UK contributes a high-energy optical laser to HED instrument” 

    XFEL bloc

    European XFEL

    New DiPOLE laser will generate pressure and temperature conditions approaching those of solar planets and exoplanets

    17 July 2015
    No Writer Credit

    The amplifier head for the DiPOLE laser. STFC/Central Laser Facility

    The Science and Technology Facilities Council (STFC) in the United Kingdom will contribute to the European XFEL an optical laser that will generate conditions similar to the interior of Earth-like exoplanets. The £8 million (approximately 11 million euro) development and construction of the laser will be funded by STFC and the Engineering and Physical Sciences Research Council, within a grant framework overseen by Professor Justin Wark at the University of Oxford.

    The so-called DiPOLE laser will provide a very high repetition rate of ten pulses per second, with each pulse having an energy of 100 J (the same energy needed to lift a kilogram weight 10 metres high). This high average energy output was gained by a technology using diode-driven amplifiers that was devised by the STFC’s Central Laser Facility (CLF), with the diodes enabling the high pulse rate.

    When a pulsed, medium-intensity optical laser hits a solid sample, a shock wave is generated that compresses matter to hundreds of thousands of atmospheres and generates very intense heat. In order to produce an energy-dense material that has similar characteristics to what is theorized to be in an Earth-like exoplanet’s interior, the DiPOLE laser’s intensity is much lower at the beginning of the pulse than at its end, which is expected to create the compression more slowly. This so-called “shockless” or “ramp” compression would result in comparatively low temperatures of a few thousand degrees at most at pressures one million to ten million times that of ambient conditions. The energy-dense samples, which last a few nanoseconds, can be examined with a single X-ray FEL pulse before they would decompress. The data from the X-ray FEL pulses will reveal information about the physical nature and chemistry of high energy density matter.

    The laser will be manufactured, assembled, and tested in the UK by CLF and will then be shipped for the final assembly in Germany. It is part of the contributions by the Helmholtz International Beamline for Extreme Fields at the European XFEL (HIBEF) user consortium and will be installed at the High Energy Density Science (HED) instrument. The UK previously has provided funding for the Serial Femtosecond Crystallography (SFX) user consortium and has stated its intention to invest up to £30 million to become the European XFEL’s twelfth member state.

    “We are delighted to be part of this ambitious endeavor”, says CLF Director Prof. John Collier. “The European XFEL project is at the frontier of X-ray science, and the CLF is at the frontier of laser & plasma science. DiPOLE showcases British laser technology at its best and, when installed on the European XFEL in 2017, will provide unprecedented opportunities for both the UK and international scientific community.”

    “We thank STFC and CLF for their engagement in this development. The user community has stated the need for a high-energy laser for compression experiments a long time ago”, says European XFEL Scientific Director Thomas Tschentscher. “The contribution by CLF, whose researchers have decades of experience in laser design and building, makes it now possible to meet this demand.”

    For more information, visit the CLF website.

    See the full article here.

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    XFEL Campus

    The Hamburg area will soon boast a research facility of superlatives: The European XFEL will generate ultrashort X-ray flashes—27 000 times per second and with a brilliance that is a billion times higher than that of the best conventional X-ray radiation sources.

    The outstanding characteristics of the facility are unique worldwide. Starting in 2017, it will open up completely new research opportunities for scientists and industrial users.

  • richardmitnick 10:13 am on May 27, 2015 Permalink | Reply
    Tags: , , , , Laser Technology,   

    From LLNL: “Lawrence Livermore scientists move one step closer to mimicking gamma-ray bursts” 

    Lawrence Livermore National Laboratory

    May. 26, 2015

    Anne M Stark
    stark8@llnl.gov (link sends e-mail)

    The Centaurus A galaxy, at a distance of about 12 million light years from Earth, contains a gargantuan jet blasting away from a central supermassive black hole. In this image, red, green and blue show low, medium and high-energy X-rays. Photo courtesy NASA/CXC/U. Birmingham/M. Burke et al.

    Using ever more energetic lasers, Lawrence Livermore researchers have produced a record high number of electron-positron pairs, opening exciting opportunities to study extreme astrophysical processes, such as black holes and gamma-ray bursts.

    By performing experiments using three laser systems — Titan at Lawrence Livermore, Omega-EP at the Laboratory for Laser Energetics (link is external) and Orion at Atomic Weapons Establishment (link is external) (AWE) in the United Kingdom — LLNL physicist Hui Chen and her colleagues created nearly a trillion positrons (also known as antimatter particles). In previous experiments at the Titan laser in 2008, Chen’s team had created billions of positrons.

    Positrons, or “anti-electrons,” are anti-particles with the same mass as an electron but with opposite charge. The generation of energetic electron-positron pairs is common in extreme astrophysical environments associated with the rapid collapse of stars and formation of black holes. These pairs eventually radiate their energy, producing extremely bright bursts of gamma rays. Gamma-ray bursts (GRBs) are the brightest electromagnetic events known to occur in the universe and can last from ten milliseconds to several minutes. The mechanism of how these GRBs are produced is still a mystery.

    In the laboratory, jets of electron-positron pairs can be generated by shining intense laser light into a gold foil. The interaction produces high-energy radiation that will traverse the material and create electron-positron pairs as it interacts with the nucleus of the gold atoms. The ability to create a large number of positrons in a laboratory, by using energetic lasers, opens the door to several new avenues of antimatter research, including the understanding of the physics underlying extreme astrophysical phenomena such as black holes and gamma-ray bursts.

    “The goal of our experiments was to understand how the flux of electron-positron pairs produced scales with laser energy,” said Chen, who along with former Lawrence Fellow Frederico Fiuza (now at SLAC National Accelerator Laboratory), co-authored the article appearing in the May 18 edition of Physical Review Letters.

    “We have identified the dominant physics associated with the scaling of positron yield with laser and target parameters, and we can now look at its implication for using it to study the physics relevant to gamma-ray bursts,” Chen said. “The favorable scaling of electron-positron pairs with laser energy obtained in our experiments suggests that, at a laser intensity and pulse duration comparable to what is available, near-future 10-kilojoule-class lasers would provide 100 times higher antimatter yield.”

    The team used these scaling results obtained experimentally together with first-principles simulations to model the interaction of two electron positron pairs for future laser parameters. “Our simulations show that with upcoming laser systems, we can study how these energetic pairs of matter-antimatter convert their energy into radiation,” Fiuza said. “Confirming these predictions in an experiment would be extremely exciting.”

    Antimatter research could reveal why more matter than antimatter survived the Big Bang at the start of the universe. There is considerable speculation as to why the observable universe is apparently almost entirely matter, whether other places are almost entirely antimatter, and what might be possible if antimatter could be harnessed. Normal matter and antimatter are thought to have been in balance in the very early universe, but due to an “asymmetry” the antimatter decayed or was annihilated, and today very little antimatter is seen.

    In future work, the researchers plan to use the National Ignition Facility [NIF] to conduct laser antimatter experiments to study the physics of relativistic pair shocks in gamma-ray bursts by creating even higher fluxes of electron-positron pairs.


    The research was funded by LLNL’s Laboratory Directed Research and Development program and the LLNL Lawrence Fellowship.

    Chen and Fiuza were joined by Anthony Link, Andy Hazi, Matt Hill, David Hoarty, Steve James, Shaun Kerr, David Meyerhofer, Jason Myatt, Jaebum Park, Yasuhiko Sentoku and Jackson Williams from LLNL, AWE, University of Alberta, University of Rochester and University of Nevada, Reno.

    See the full article here.

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    Operated by Lawrence Livermore National Security, LLC, for the Department of Energy’s National Nuclear Security
    DOE Seal

  • richardmitnick 8:26 am on May 15, 2015 Permalink | Reply
    Tags: , , , Laser Technology,   

    From BNL: “Intense Lasers Cook Up Complex, Self-Assembled Nanomaterials” 

    Brookhaven Lab

    May 13, 2015
    Justin Eure

    New technique developed at Brookhaven Lab makes self-assembly 1,000 times faster and could be used for industrial-scale solar panels and electronics

    Brookhaven Lab scientist Kevin Yager (left) and postdoctoral researcher Pawel Majewski with the new Laser Zone Annealing instrument at the Center for Functional Nanomaterials.

    Nanoscale materials feature extraordinary, billionth-of-a-meter qualities that transform everything from energy generation to data storage. But while a nanostructured solar cell may be fantastically efficient, that precision is notoriously difficult to achieve on industrial scales. The solution may be self-assembly, or training molecules to stitch themselves together into high-performing configurations.

    Now, scientists at the U.S. Department of Energy’s Brookhaven National Laboratory have developed a laser-based technique to execute nanoscale self-assembly with unprecedented ease and efficiency.

    “We design materials that build themselves,” said Kevin Yager, a scientist at Brookhaven’s Center for Functional Nanomaterials (CFN). “Under the right conditions, molecules will naturally snap into a perfect configuration. The challenge is giving these nanomaterials the kick they need: the hotter they are, the faster they move around and settle into the desired formation. We used lasers to crank up the heat.”

    Yager and Brookhaven Lab postdoctoral researcher Pawel Majewski built a one-of-a-kind machine that sweeps a focused laser-line across a sample to generate intense and instantaneous spikes in temperature. This new technique, called Laser Zone Annealing (LZA), drives self-assembly at rates more than 1,000 times faster than traditional industrial ovens. The results are described in the journal ACS Nano.

    “We created extremely uniform self-assembled structures in less than a second,” Majewski said. “Beyond the extraordinary speed, our laser also reduced the defects and degradations present in oven-heated materials. That combination makes LZA perfect for carrying small-scale laboratory breakthroughs into industry.”

    The scientists prepared the materials and built the LZA instrument at the CFN. They then analyzed samples using advanced electron microscopy at CFN and x-ray scattering at Brookhaven’s now-retired National Synchrotron Light Source (NSLS)—both DOE Office of Science User Facilities.

    “It was enormously gratifying to see that our predictions were accurate—the enormous thermal gradients led to a correspondingly enormous acceleration!” Yager said.

    Illustration of the Lazer Zone Annealing instrument showing the precise laser (green) striking the un-assembled polymer (purple). The extreme thermal gradients produced by the laser sweeping across the sample cause rapid and pristine self-assembly.

    Ovens versus lasers

    Imagine preparing a complex cake, but instead of baking it in the oven, a barrage of lasers heats it to perfection in an instant. Beyond that, the right cooking conditions will make the ingredients mix themselves into a picture-perfect dish. This nanoscale recipe achieves something equally extraordinary and much more impactful.

    The researchers focused on so-called block copolymers, molecules containing two linked blocks with different chemical structures and properties. These blocks tend to repel each other, which can drive the spontaneous formation of complex and rigid nanoscale structures.

    “The price of their excellent mechanical properties is the slow kinetics of their self-assembly,” Majewski said. “They need energy and time to explore possibilities until they find the right configuration.”

    In traditional block copolymer self-assembly, materials are heated in a vacuum-sealed oven. The sample is typically “baked” for a period of 24 hours or longer to provide enough kinetic energy for the molecules to snap into place—much too long for commercial viability. The long exposure to high heat also causes inevitable thermal degradation, leaving cracks and imperfections throughout the sample.

    The LZA process, however, offers sharp spikes of heat to rapidly excite the polymers without the sustained energy that damages the material.

    “Within milliseconds, the entire sample is beautifully aligned,” Yager said. “As the laser sweeps across the material, the localized thermal spikes actually remove defects in the nanostructured film. LZA isn’t just faster, it produces superior results.”

    LZA generates temperatures greater than 500 degrees Celsius, but the thermal gradients—temperature variations tied to direction and location in a material—can reach more than 4,000 degrees per millimeter. While scientists know that higher temperatures can accelerate self-assembly, this is the first proof of dramatic enhancement by extreme gradients.

    Built from scratch

    “Years ago, we observed a subtle hint that thermal gradients could improve self-assembly,” Yager said. “I became obsessed with the idea of creating more and more extreme gradients, which ultimately led to building this laser setup, and pioneering a new technique.”

    The researchers needed a high concentration of technical expertise and world-class facilities to move the LZA from proposal to execution.

    “Only at the CFN could we develop this technique so quickly,” Majewski said. “We could do rapid instrument prototyping and sample preparation with the on-site clean room, machine shop, and polymer processing lab. We then combined CFN electron microscopy with x-ray studies at NSLS for an unbeatable evaluation of the LZA in action.”

    Added Yager, “The ability to make new samples at the CFN and then walk across the street to characterize them in seconds at NSLS was key to this discovery. The synergy between these two facilities is what allowed us to rapidly iterate to an optimized design.”

    The scientists also developed a new microscale surface thermometry technique called melt-mark analysis to track the exact heat generated by the laser pulses and tune the instrument accordingly.

    “We burned a few films initially before we learned the right operating conditions,” Majewski said. “It was really exciting to see the first samples being rastered by the laser and then using NSLS to discover exactly what happened.”

    Future of the technique

    The LZA is the first machine of its kind in the world, but it signals a dramatic step forward in scaling up meticulously designed nanotechnology. The laser can even be used to “draw” structures across the surface, meaning the nanostructures can assemble in well-defined patterns. This unparalleled synthesis control opens the door to complex applications, including electronics.

    “There’s really no limit to the size of a sample this technique could handle,” Yager said. “In fact, you could run it in a roll-to-roll mode—one of the leading manufacturing technologies.”

    The scientists plan to further develop the new technique to create multi-layer structures that could have immediate impacts on anti-reflective coatings, improved solar cells, and advanced electronics.

    This research and operations at CFN and NSLS were funded by the DOE Office of Science.

    See the full article here.

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    BNL Campus

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

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