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  • richardmitnick 12:09 pm on November 15, 2017 Permalink | Reply
    Tags: A Speed Gun for Photosynthesis, A type of optical sensor that if the science bears out will be able to estimate the rate of photosynthesis, , , , NIST, SIF - Solar Induced Fluorescence, Specially designed sap flow sensors, Such aDevice would revolutionize agriculture forestry and the study of Earth’s climate and ecosystems   

    From NIST: “A Speed Gun for Photosynthesis” 


    NIST

    1
    The NIST forest in Gaithersburg, Maryland. Credit: R. Press/NIST

    November 03, 2017 [NIST is not always quick to social media]
    Rich Press

    On a recent sunny afternoon, David Allen was standing by a third-floor window in a research building at the National Institute of Standards and Technology (NIST), holding in his hands a device that looked like a cross between a video camera and a telescope. The NIST campus is in suburban Gaithersburg, Maryland, but looking out the window, Allen could see 24 hectares (60 acres) of tulip tree, oak, hickory and red maple—a remnant of the northeastern hardwood forest that once dominated this landscape.

    Allen mounted the device on a tripod and pointed it out the window at the patch of forest below. The device wasn’t a camera, but a type of optical sensor that, if the science bears out, will be able to estimate the rate of photosynthesis—the chemical reaction that enables plants to convert water, carbon dioxide (CO2) and sunlight into food and fiber—from a distance.

    That measurement is possible because when plants are photosynthesizing, their leaves emit a very faint glow of infrared light. That glow is called Solar Induced Fluorescence, or SIF, and in recent years, optical sensors for measuring it have advanced dramatically. The sensor that Allen had just mounted on a tripod was one of them.

    “If SIF sensors end up working well,” Allen said, “I can imagine an instrument that stares at crops or a forest and has a digital readout on it that says how fast the plant is growing in real time.”

    Such a device would revolutionize agriculture, forestry and the study of Earth’s climate and ecosystems.

    2
    NIST scientist David Allen and Boston University Ph.D. student Julia Marrs aim a SIF sensor at a specific tree in the NIST forest.
    Credit: R. Press/NIST

    Allen is a NIST chemist whose research involves remote sensing—the technology that’s used to observe Earth from outer space. Remote sensing allows scientists to track hurricanes, map terrain, monitor population growth and produce daily weather reports. The technology is so deeply embedded in our everyday lives that it’s easy to take for granted. But each type of remote sensing had to be developed from the ground up, and the SIF project at NIST shows how that’s done.

    Some satellites are already collecting SIF data, but standards are needed to ensure that those measurements can be properly interpreted. NIST has a long history of developing standards for satellite-based measurements, and Allen’s research is aimed at developing standards for measuring SIF. Doing that requires a better understanding of the biological processes that underlie SIF, and for that, Allen teamed up with outside scientists.

    At the same time that Allen was aiming a SIF sensor through that third-floor window, a team of biologists from Boston University and Bowdoin College was in the NIST forest measuring photosynthesis up close. A pair of them spent the day climbing into the canopy on an aluminum orchard ladder. Once there, they would use a portable gas exchange analyzer to measure photosynthesis directly based on how much CO2 the leaf pulled out of the air. They also measured SIF at close range.

    3
    Boston University ecologist Lucy Hutyra (left) works at the forest edge alongside plant physiological ecologist Barry Logan (center) and ecologist Jaret Reblin, both of Bowdoin College in Brunswick, Maine. They measured photosynthesis directly, as well as temperature, humidity, and other environmental variables. Credit: R. Press/NIST

    Other scientists checked on specially designed sap flow sensors they had installed on the trunks of trees to measure the movement of water toward the leaves for photosynthesis.

    “We’re measuring the vital signs of the trees,” said Lucy Hutyra, the Boston University ecologist who led the team of scientists on the ground. The idea was to use those ground measurements to make sense of the SIF data collected from a distance.

    “If we measure an increase in photosynthesis at the leaf, we should see a corresponding change in the optical signal,” Hutyra said.

    4
    After directly measuring photosynthesis in an individual leaf using a field portable gas exchange analyzer, scientists preserved a small sample of leaf tissue in liquid nitrogen. They would later analyze that tissue in the lab to measure levels of chlorophyll and other pigments. Credit: R. Press/NIST

    The research was also taking place at still a higher level. That afternoon, Bruce Cook and Larry Corp, scientists with NASA’s G-LiHT project, flew over the NIST forest in a twin-turboprop plane that carried multiple sensors, including a SIF sensor and Light Detection and Ranging (LiDAR) sensors that mapped the internal structure of the forest canopy. The aircraft made six parallel passes over the forest at about 340 meters (1,100 feet, slightly above the minimum safe altitude allowed by FAA regulations), the instruments peering out from a port cut into the belly of the aircraft.

    That gave the scientists three simultaneous measurements to work with: from the ground, from the window above the forest and from the air. They’ll spend months correlating the data.

    “It’s tricky, because when you go from the leaf level to the forest level, you often get different results,” Allen said. For instance, at the forest level, the SIF signal is affected by the variations in the canopy, including its contours and density. “We’re still studying those effects.”

    5
    At the airport in Gaithersburg, Maryland, NASA earth scientist Bruce Cook (left), leader of the Goddard LiDAR, Hyperspectral, and Thermal (G-LiHT) project, shows David Allen and Julia Marrs the sensor array in the bottom of the aircraft. Credit: R. Press/NIST

    Currently, there is no reliable way to measure photosynthesis in real time over a wide area. Instead, scientists measure how green an area is to gauge how much chlorophyll is present—that’s the molecule that supports photosynthesis and gives leaves their color. But if a plant lacks water or nutrients, it may be green even if the photosynthetic machinery is switched off.

    SIF may be a much better indicator of active photosynthesis. When plants are photosynthesizing, most of the light energy absorbed by the chlorophyll molecule goes into growing the plant, but about two to five percent of that energy leaks away as SIF. The amount of leakage is not always proportional to photosynthesis, however. Environmental variables also come into play.

    The NIST forest is a test bed for understanding how all those variables interrelate. In addition to SIF data and the vital signs of trees, the scientists are collecting environmental data such as temperature, relative humidity and solar irradiance. They’re also figuring out the best ways to configure and calibrate the SIF instruments.

    “We’d like to see robust, repeatable results that make sense,” Allen said. “That will allow us to scale up from the leaf level, to the forest level, to the ecosystem level, and to estimate photosynthesis from measurements made at any of those scales.”

    Making SIF scalable is a key part of the measurement standard that Allen is working to create, and it will go from the ground level to measurements made from outer space.

    6
    A corner of the NIST forest shot by NASA scientists, and the plane that carried them and their G-LiHT airborne imaging system.
    Credit: Bruce Cook, Larry Corp/NASA (left); David Allen/NIST

    Using SIF to measure photosynthesis in real time would allow farmers to use only as much irrigation and fertilizer as their crops need, and only when they need it. Forest managers would be able to know how fast their timber is growing without having to tromp through the woods with a tape measure. Environmental managers would be able to monitor the recovery of damaged or deforested habitats after a drought or forest fire.

    And scientists would have a powerful new tool for studying how plants help regulate the amount of CO2 in the atmosphere.

    Humans add CO2 to the atmosphere when they burn fossil fuels, and land-based plants remove roughly a quarter of that CO2 through photosynthesis. But the environmental factors that affect that process are not well understood, mainly because scientists haven’t had a good way to measure the uptake of CO2 at the ecosystem level. SIF measurements, and the standards for interpreting them accurately, might help solve that problem.

    “CO2 exchange by plants is one of the most important biological processes on the planet,” Allen said, “and SIF will give us a new way to see that process in action.”

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    NIST Campus, Gaitherberg, MD, USA

    NIST Mission, Vision, Core Competencies, and Core Values

    NIST’s mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

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  • richardmitnick 1:30 pm on November 14, 2017 Permalink | Reply
    Tags: , “Lamp-plaque” method, , FELs, Hyperspectral cameras are used for a wide range of monitoring applications including biomedical defense and ground-based air-based and space-based environmental sensing, Lights Camera Calibrate! Improving Space Cameras with a Better Model for Ultra-Bright Lamps, NIST, , There’s an emerging market for hyperspectral sensors in general   

    From NIST: “Lights, Camera, Calibrate! Improving Space Cameras with a Better Model for Ultra-Bright Lamps” 


    NIST

    November 14, 2017
    Jennifer Lauren Lee

    1
    A standard FEL lamp, such as the one pictured here, is about the size of a person’s thumb. Credit: David Allen/NIST

    Studio photographers may be familiar with the 1,000-watt quartz halogen lamps known as “FELs.” Scientists use them too—specially calibrated ones, at least—to test the performance of light sensors that monitor Earth’s weather, plant life and oceans, often from space.

    A researcher at the National Institute of Standards and Technology (NIST) has recently made an improved mathematical model of the light output of FEL lamps. The new model, developed by NIST theorist Eric Shirley, will make the lamps more useful research tools, the scientists say, particularly for calibrating a relatively new class of cameras called hyperspectral imagers.

    Rainbow Vision

    Hyperspectral cameras are used for a wide range of monitoring applications, including biomedical, defense, and ground-based, air-based and space-based environmental sensing. While ordinary cameras only capture light in three bands of wavelengths—red, green and blue—hyperspectral imagers can be designed to see all the colors of the rainbow and beyond, including ultraviolet and infrared. Their increased range allows these cameras to reveal the distinctive signatures of processes that are invisible to the naked eye.

    Some of these effects are subtle, however—such as when researchers are trying to tease out changes in ocean color, or to monitor plant growth, which helps them predict crop productivity.

    “These are both examples where you’re looking at an extremely small signal of just a couple percent total,” said David Allen of NIST’s Physical Measurement Laboratory (PML). In cases like this, achieving low uncertainties in the calibration of their detectors is essential.

    Of particular interest to Allen and his colleagues was a calibration technique called the “lamp-plaque” method, popular with scientists because it is relatively inexpensive and portable. For this calibration procedure, researchers use a standard FEL lamp. Incidentally, FEL is the name designated by the American National Standards Institute (ANSI) for these lamps. It is not an acronym.

    First, the lamp light shines onto a white, rectangular board called a reflectance plaque, made of a material that scatters more than 99 percent of the visible, ultraviolet and near-infrared light that hits it. Then, after bouncing off the plaque, the scattered light hits the camera being calibrated.

    The method has been used for decades to calibrate other kinds of sensors, which only need to see one point of light. Hyperspectral imagers, on the other hand, can distinguish shapes.

    “They have some field of view, like a camera,” Allen said. “That means that to calibrate them, you need something that illuminates a larger area.” And the trouble with the otherwise convenient lamp-plaque system is that the light bouncing off the plaque isn’t uniform: It’s brightest in the center and less intense toward the edges.

    The researchers could easily calculate the intensity of the light in the brightest spot, but they didn’t know exactly how that light falls off in brightness toward the plaque’s edges.

    To lower the calibration uncertainties, researchers needed a better theoretical model of the lamp-plaque system.

    Counting Coils

    Shirley, the NIST theorist who took on this task, had to consider several parameters. One major contributor to the variations in intensity is the orientation of the lamp with respect to the plaque. FEL lamps have a filament that consists of a coiled coil—the shape that an old-fashioned telephone cord would make if wrapped around a finger. All that coiling means that light produced by one part of the filament can be physically blocked by other parts of the filament. Setting the lamp at an angle with respect to the plaque exacerbates this effect.

    2
    Close-up of an FEL lamp revealing its “coiled coil” filament. Behind the lamp is a white reflectance plaque like the ones used in calibrations. Credit: Jennifer Lauren Lee/NIST

    To model the system, Shirley took into account the diameter of the wire and both coils, the amount of space between each curve of the coils and the distance between the lamp and the plaque.

    “These are all things that were obvious,” Shirley said, “but they were not as appreciated before.”

    NIST scientists tested the actual output of some FEL lamp-plaque systems against what the model predicted and found good agreement. They say the uncertainties on light intensity across the entire plaque could now be as low as a fraction of a percent, down from about 10 to 15 percent.

    Moving forward, NIST will incorporate the new knowledge into its calibration service for hyperspectral imagers. But researchers are preparing to publish their results and hope scientists will use the new model when doing their own calibrations. The work could also serve as a foundation for creating better detector specifications, potentially useful for U.S. manufacturers who build and sell the cameras.

    “There’s an emerging market for hyperspectral sensors in general,” Allen said. “They’re becoming more sophisticated, and this is a component to help them be a more robust product in an increasingly competitive market.”

    Sensors, Modeling & simulation research, Optical / photometry / laser metrology, Physics and Standards

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    NIST Campus, Gaitherberg, MD, USA

    NIST Mission, Vision, Core Competencies, and Core Values

    NIST’s mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

     
  • richardmitnick 9:42 am on November 8, 2017 Permalink | Reply
    Tags: An entirely new model of the way electrons are briefly trapped and released in tiny electronic devices suggests that a long-accepted industry-wide view is just plain wrong about the way these captured, , As you get down to the very smallest sizes RTN can be nearly 100 percent as strong as the signal you’re trying to measure, Charge trapping is one of the known causes of flash memory failure, MOSFET, NIST, RTN noise, The noise is caused by the action of electrons near the interface between two materials such as an insulator layer and the bulk of the semiconductor in a transistor   

    From NIST: “New Insights on ‘Captured’ Electrons Could Improve Flash Memory” 


    NIST

    November 07, 2017

    Media Contact
    Ben Stein
    benjamin.stein@nist.gov
    (301) 975-2763

    Technical Contact
    Kin (Charles) Cheung
    kin.cheung@nist.gov
    (301) 975-3093

    1
    No image caption or credit

    An entirely new model of the way electrons are briefly trapped and released in tiny electronic devices suggests that a long-accepted, industry-wide view is just plain wrong about the way these captured electrons affect the behavior of hardware components such as flash memory cells.

    The model, devised by scientists at the National Institute of Standards and Technology (NIST), was tested to explain how electron capture and emission creates the insidious noise that increasingly threatens performance as electronic devices continue to shrink in size.

    Those effects, variously known as burst noise, popcorn noise or random telegraph noise (RTN) “have become a major problem for extremely small devices,” said NIST researcher Kin Cheung, the lead author of a new report in IEEE Transactions on Electron Devices .

    Charge trapping is one of the known causes of flash memory failure. The new model, which NIST physicist John Kramar called “a major paradigm shift in charge-trapping modeling,” could lead to a different approach to manage this problem, and potentially, a new way of making the memory cells smaller.

    RTN noise consists of abrupt random drops in voltage or current caused by itinerant electrons that are briefly captured from, and then rejoin, the main flow along a current channel in, for example, a common type of transistor called a MOSFET.

    “The effect was mostly negligible back in the good old days when devices were larger and there were lots of electrons flowing around,” Cheung said. But in today’s advanced devices, with feature dimensions in the range of 10 nanometers (nm, billionths of a meter) or less, the active area is so small that it can be swamped by a single trapped charge.

    “As you get down to the very smallest sizes, RTN can be nearly 100 percent as strong as the signal you’re trying to measure,” Cheung said. “In those conditions, reliability disappears.”

    In the case of RTN, the basics are known: The noise is caused by the action of electrons near the interface between two materials such as an insulator layer and the bulk of the semiconductor in a transistor. Specifically, an electron is pulled out of the current flow and trapped in a defect in the insulator; after a short time, it is emitted back into the main current in the semiconductor. What actually happens on the atomic scale at each stage of the process, however, is incompletely understood.

    The orthodox approach to account for those effects is to treat all the trapped electrons as a single 2-D sheet of charge that extends uniformly across the center of the insulator. Each emitted electron is thought to return to the semiconductor in a reverse of the same process by which it was captured, causing very little change in the presumably stable state along the insulator/semiconductor boundary.

    That model, when applied to very small devices, didn’t make sense to the NIST scientists. Among other difficulties, it ignored the fact that, once they are immobilized, electrons cause considerable distortions in local electrical field conditions along the boundary, affecting current flow. “We’re saying the traditional way doesn’t really work,” Cheung said. “You have to rethink this thing. The old model doesn’t make reasonable assumptions about how charge carriers behave.”

    2
    No image caption or credit

    The researchers proposed a new model, based on local effects, in which the mechanisms of capture and emission are dramatically different from the standard picture. For one thing, they determined that quantum mechanics, the modern theory that describes the behavior of these systems, makes it hugely improbable, if not impossible, for electrons to get out of the insulator the same way they got in.

    “It’s like a highway where there is an exit ramp, but there’s no on ramp,” says NIST co-author Jason Campbell. “You can go in, but you can’t come back that way. You’ve got to come back a different way. That is, there is a set of rules for capture that don’t apply to emission.”

    “When you realize that the capture and emission processes are decoupled,” Cheung said, “you quickly have a very different view of the problem.”

    The standard RTN picture supposes a weak interaction of trapped charge with its local surroundings―in this case, the highly separated electric charge in the silicon dioxide that often makes up the insulator layer in a transistor. NIST scientists found that a weak interaction is inconsistent with known physics and not in agreement with reports from two independent laboratories. Indeed, the interaction energy of a captured electron can be more than 10 times greater than previously believed. Recognition of this stronger interaction energy enables the new local field picture to explain RTN naturally.

    The success of the new model, and the resulting drastic change in the understanding of both capture and emission, suggested that many long-held ideas would have to be thoroughly reconsidered.

    “That was a very scary, very unsettling conclusion,” Campbell said. “I mean, this is tear-up-the-textbook stuff.”

    The researchers hope the new model will help chip engineers and designers understand in much greater detail how devices degrade, and what will be required to get to the next stage of miniaturization while maintaining reliability and reducing noise.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    NIST Campus, Gaitherberg, MD, USA

    NIST Mission, Vision, Core Competencies, and Core Values

    NIST’s mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

     
  • richardmitnick 5:33 pm on November 7, 2017 Permalink | Reply
    Tags: A way to link a group of atoms’ quantum mechanical properties among themselves far more quickly than is currently possible potentially providing a tool for highly precise sensing and quantum compute, , Dipolar interaction, Getting the atoms into an entangled state more quickly would be a potential advantage in any practical application not least because entanglement can be fleeting, Need Entangled Atoms? Get 'Em FAST! With NIST’s New Patent-Pending Method, NIST, , , Uncertainty is the key here   

    From NIST: “Need Entangled Atoms? Get ‘Em FAST! With NIST’s New Patent-Pending Method” 


    NIST

    November 07, 2017

    Chad Boutin
    boutin@nist.gov
    (301) 975-4261

    1
    While quantum entanglement usually spreads through the atoms in an optical lattice via short-range interactions with the atoms’ immediate neighbors (left), new theoretical research shows that taking advantage of long-range dipolar interactions among the atoms could enable it to spread more quickly (right), a potential advantage for quantum computing and sensing applications.
    Credit: Gorshkov and Hanacek/NIST

    Physicists at the National Institute of Standards and Technology (NIST) have come up with a way to link a group of atoms’ quantum mechanical properties among themselves far more quickly than is currently possible, potentially providing a tool for highly precise sensing and quantum computer applications. NIST has applied for a patent on the method, which is detailed in a new paper in Physical Review Letters.

    The method, which has not yet been demonstrated experimentally, essentially would speed up the process of quantum entanglement in which the properties of multiple particles become interconnected with one other. Entanglement would propagate through a group of atoms in dramatically less time, allowing scientists to build an entangled system exponentially faster than is common today.

    Arrays of entangled atoms suspended in laser light beams, known as optical lattices, are one approach to creating the logic centers of prototype quantum computers, but an entangled state is difficult to maintain more than briefly. Applying the method to these arrays could give scientists precious time to do more with these arrays of atoms before entanglement is lost in a process known as decoherence.

    The method takes advantage of a physical relationship among the atoms called dipolar interaction, which allows atoms to influence each other over greater distances than previously possible. The research team’s Alexey Gorshkov compares it to sharing tennis balls among a group of people. While previous methods essentially allowed people to pass tennis balls only to a person standing next to them, the new approach would allow an individual to toss them to people across the room.

    “It is these long-range dipolar interactions in 3-D that enable you to create entanglement much faster than in systems with short-range interactions,” said Gorshkov, a theoretical physicist at NIST and at both the Joint Center for Quantum Information and Computer Science and the Joint Quantum Institute, which are collaborations between NIST and the University of Maryland. “Obviously, if you can throw stuff directly at people who are far away, you can spread the objects faster.”

    Applying the technique would center around adjusting the timing of laser light pulses, turning the lasers on and off in particular patterns and rhythms to quick-change the suspended atoms into a coherent entangled system.

    The approach also could find application in sensors, which might exploit entanglement to achieve far greater sensitivity than classical systems can. While entanglement-enhanced quantum sensing is a young field, it might allow for high-resolution scanning of tiny objects, such as distinguishing slight temperature differences among parts of an individual living cell or performing magnetic imaging of its interior.

    Gorshkov said the method builds on two studies from the 1990s in which different NIST researchers considered the possibility of using a large number of tiny objects—such as a group of atom—as sensors. Atoms could measure the properties of a nearby magnetic field, for example, because the field would change their electrons’ energy levels. These earlier efforts showed that the uncertainty in these measurements would be advantageously lower if the atoms were all entangled, rather than merely a bunch of independent objects that happened to be near one another.

    “Uncertainty is the key here,” said Gorshkov. “You want that uncertainty as low as possible. If the atoms are entangled, you have less uncertainty about that magnetic field’s magnitude.”

    Getting the atoms into an entangled state more quickly would be a potential advantage in any practical application, not least because entanglement can be fleeting.

    When a group of atoms is entangled, the quantum state of each one is bound up with the others so that the entire system possesses a single quantum state. This connection can exist even if the atoms are separated and completely isolated from one another (giving rise to Einstein’s famous description of it as “spooky action at a distance”), but entanglement is also quite a fragile condition. The difficulty of maintaining it among large numbers of atoms has slowed the development of entanglement-based technologies such as quantum computers.

    “Entangled states tend to decohere and go back to being a bunch of ordinary independent atoms,” Gorshkov said. “People knew how to create entanglement, but we looked for a way to do it faster.”

    If the method can be experimentally demonstrated, it could give a quantum computer’s processor additional time so it can outpace decoherence, which threatens to make a computation fall apart before the qubits can finish their work. It would also reduce the uncertainty if used in sensing applications.

    “We think this is a practical way to increase the speed of entanglement,” Gorshkov said. “It was cool enough to patent, so we hope it proves commercially useful to someone.”

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    NIST Campus, Gaitherberg, MD, USA

    NIST Mission, Vision, Core Competencies, and Core Values

    NIST’s mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

     
  • richardmitnick 5:05 pm on November 7, 2017 Permalink | Reply
    Tags: , Color me Purple or Red or Green or …, Directional color filter ruled with grooves that are not uniformly spaced, , NIST,   

    From NIST: “Color me Purple, or Red, or Green, or … “ 


    NIST

    November 07, 2017

    Ben Stein
    benjamin.stein@nist.gov
    (301) 975-2763

    1
    Schematic shows two different ways that white light interacts with a newly developed device, a directional color filter ruled with grooves that are not uniformly spaced. When white light illuminates the patterned side of the compact metal device at three different angles—in this case, 0° degrees, 10° and 20°—the device transmits light at red, green and blue wavelengths, respectively. When white light incident at any angle illuminates the device from the non-patterned side, it separates the light into the same three colors, and sends off each color in different directions corresponding to the same respective angles. Credit: NIST

    Imagine a miniature device that suffuses each room in your house with a different hue of the rainbow—purple for the living room, perhaps, blue for the bedroom, green for the kitchen. A team led by scientists at the National Institute of Standards and Technology (NIST) has, for the first time, developed nanoscale devices that divide incident white light into its component colors based on the direction of illumination, or directs these colors to a predetermined set of output angles.

    Viewed from afar, the device, referred to as a directional color filter, resembles a diffraction grating, a flat metal surface containing parallel grooves or slits that split light into different colors. However, unlike a grating, the nanometer-scale grooves etched into the opaque metal film are not periodic—not equally spaced. They are either a set of grooved lines or concentric circles that vary in spacing, much smaller than the wavelength of visible light. These properties shrink the size of the filter and allow it to perform many more functions than a grating can.

    For instance, the device’s nonuniform, or aperiodic, grid can be tailored to send a particular wavelength of light to any desired location. The filter has several promising applications, including generating closely spaced red, green and blue color pixels for displays, harvesting solar energy, sensing the direction of incoming light and measuring the thickness of ultrathin coatings placed atop the filter.

    In addition to selectively filtering incoming white light based on the location of the source, the filter can also operate in a second way. By measuring the spectrum of colors passing through a filter custom-designed to deflect specific wavelengths of light at specific angles, researchers can pinpoint the location of an unknown source of light striking the device. This could be critical to determine if that source, for instance, is a laser aimed at an aircraft.

    “Our directional filter, with its aperiodic architecture, can function in many ways that are fundamentally not achievable with a device such as a grating, which has a periodic structure,” said NIST physicist Amit Agrawal. “With this custom-designed device, we are able to manipulate multiple wavelengths of light simultaneously.”

    Matthew Davis and Wenqi Zhu of NIST and the University of Maryland, along with Agrawal and NIST physicist Henri Lezec, described their work in the latest edition of Nature Communications. The work was performed in collaboration with Syracuse University and Nanjing University in China.

    The operation of the directional color filter relies on the interaction between the incoming particles of light—photons—and the sea of electrons that floats along the surface of a metal. Photons striking the metal surface create ripples in this electron sea, generating a special type of light wave—plasmons—that has a much smaller wavelength than the original light source.

    The design and operation of aperiodic devices are not as intuitive and straightforward as their periodic counterparts. However, Agrawal and his colleagues have developed a simple model for designing these devices. Lead author Matthew Davis explained, “this model allows us to quickly predict the optical response of these aperiodic designs without relying on time-consuming numerical approximation, thereby greatly decreasing the design time so we can focus on device fabrication and testing.”

    The work described in the new paper was conducted at NIST’s Center for Nanoscale Science and Technology.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    NIST Campus, Gaitherberg, MD, USA

    NIST Mission, Vision, Core Competencies, and Core Values

    NIST’s mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

     
  • richardmitnick 4:45 pm on November 7, 2017 Permalink | Reply
    Tags: , NIST, , , Quantum photonic circuits, Waveguides   

    From NIST: “Hybrid Circuit Combines Single-Photon Generator and Efficient Waveguides on One Chip” 


    NIST

    November 07, 2017

    Ben Stein
    benjamin.stein@nist.gov
    (301) 975-2763

    New architecture could prove essential for high-performance quantum photonic circuits.

    1
    The architecture of this hybrid quantum photonic circuit is among the first to combine on a single chip a reliable generator of individual photons—a quantum dot (red dot), here embedded in gallium arsenide (yellow)—with passive elements such as a low-loss waveguide (purple) that transports the photons. Credit: NIST

    Scientists at the National Institute of Standards and Technology (NIST) and their collaborators have taken a new step forward in the quest to build quantum photonic circuits—chip-based devices that rely on the quantum properties of light to process and communicate information rapidly and securely.

    The quantum circuit architecture devised by the team is among the first to combine two different types of optical devices, made from different materials, on a single chip—a semiconductor source that efficiently generates single particles of light (photons) on demand, and a network of “waveguides” that transports those photons across the circuit with low loss. Maximizing the number of photons, ideally having identical properties, is critical to enabling applications such as secure communication, precision measurement, sensing and computation, with potentially greater performance than that of existing technologies.

    The architecture, developed by Marcelo Davanco and other NIST researchers along with collaborators from China and the U.K., employs a nanometer-scale semiconductor structure called a quantum dot—made from indium arsenide—to generate individual photons on the same chip as the optical waveguides—made from silicon nitride. Combining these two materials requires special processing techniques. Such hybrid circuit architectures could become building blocks for more complex systems.

    Previously, quantum integrated photonic circuits typically consisted of only passive devices such as waveguides and beam splitters, which let photons through or allowed them to coalesce. The photons themselves still had to be produced outside the chip, and getting them onto the chip resulted in losses, which significantly degraded the performance of the circuit. Circuit architectures that did include quantum light generation on a chip either incorporated sources that only produced photons randomly and at low rates—which limits performance—or had sources in which one photon was not necessarily identical with the next. In addition, the fabrication processes supporting these previous architectures made it difficult to scale up the number, size and complexity of the photonic circuits.

    In contrast, the new architecture and the fabrication processes the team developed should enable researchers to reliably build larger circuits, which could perform more complex computations or simulations and translate into higher measurement precision and detection sensitivity in other applications.

    The quantum dot employed by the team is a well-studied nanometer-scale structure: an island of the semiconductor indium arsenide surrounded by gallium arsenide. The indium arsenide/gallium arsenide nanostructure acts as a quantum system with two energy levels—a ground state (lower energy level) and an excited state (higher energy level). When an electron in the excited state loses energy by dropping down to the ground state, it emits a single photon.

    Unlike most types of two-level emitters that exist in the solid state, these quantum dots have been shown to generate—reliably, on demand, and at large rates—the single photons needed for quantum applications. In addition, researchers have been able to place them inside nanoscale, light-confining spaces that allow a large speedup of the single-photon emission rate, and in principle, could also allow the quantum dot to be excited by a single photon. This enables the quantum dots to directly assist with the processing of information rather than simply produce streams of photons.

    The other part of the team’s hybrid circuit architecture consists of passive waveguides made of silicon nitride, known for their ability to transmit photons across a chip’s surface with very low photon loss. This allows quantum-dot-generated photons to efficiently coalesce with other photons at a beam splitter, or interact with other circuit elements such as modulators and detectors.

    “We’re getting the best of both worlds, with each behaving really well together on a single circuit,” said Davanco. In fact, the hybrid architecture keeps the high performance achieved in devices made exclusively of each of the two materials, with little degradation when they are put together. He and his colleagues described the work (link is external) in a recent issue of Nature Communications.

    To make the hybrid devices, Davanco and his colleagues first bonded two wafers together—one containing the quantum dots, the other containing the silicon nitride waveguide material. They used a variation of a process that had originally been developed for making hybrid photonic lasers, which combined silicon for waveguides and compound semiconductors for classical light emission. Once the bonding was finished, the two materials were then sculpted with nanometer-scale resolution into their final geometries through state-of-the-art semiconductor device patterning and etching techniques.

    Although this wafer bonding technique was developed more than a decade ago by other researchers, the team is the first to apply it towards making integrated quantum photonic devices.

    “Since we have expertise in both fabrication and quantum photonics, it seemed clear that we could borrow and adapt this process to create this new architecture,” notes Davanco.

    This work was performed in part at NIST’s Center for Nanoscale Science and Technology (CNST), a shared-use facility available to researchers from industry, academia and government, and also included researchers from NIST’s Physical Measurement Laboratory.

    Science paper:
    Heterogeneous integration for on-chip quantum photonic circuits with single quantum dot devices. Nature Communications.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    NIST Campus, Gaitherberg, MD, USA

    NIST Mission, Vision, Core Competencies, and Core Values

    NIST’s mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

     
  • richardmitnick 1:36 pm on September 12, 2017 Permalink | Reply
    Tags: , NIST, NIST Researchers Revolutionize the Atomic Force Microscope, PTIR-Photothermal induced resonance   

    From NIST: “NIST Researchers Revolutionize the Atomic Force Microscope” 


    NIST

    September 12, 2017

    Ben Stein
    benjamin.stein@nist.gov
    (301) 975-2763

    `
    Close-up schematic view of a nanoscale AFM probe integrated with an optical resonator to expand the probe’s capabilities. The waveguide acts as an optical version of a “whispering gallery” that allows certain frequencies of light to resonate.
    Credit: NIST

    Most measuring instruments are limited by the tradeoff between how precisely and how rapidly a measurement is made: the more precise the measurement, the longer it takes. But because many phenomena occurring at the nanoscale are both rapid and tiny, they demand a measuring system that can capture their precise details in both time and space.

    Taking up that challenge, researchers at the National Institute of Standards and Technology (NIST) have redesigned the detection system at the heart of the atomic force microscope (AFM). A premier tool of the nanoworld, the AFM uses a small probe, or tip, to map the submicroscopic hills and valleys that define the surface of materials, along with other properties, at the nanometer scale. Although the AFM has already revolutionized the understanding of nanostructures, scientists are now eager to study nanoscale phenomena, such as the folding of proteins or the diffusion of heat, which happen too quickly and generate changes too small to be accurately measured by existing versions of the microscope.

    By fabricating an extremely lightweight AFM probe and combining it with a nanoscale device that converts minuscule deflections of the probe into large changes of an optical signal inside a waveguide, the NIST researchers have broken new ground: Their AFM system measures rapid changes in structure with high precision.

    2
    Illustration of a newly fabricated atomic force microscope (AFM) probe integrated with an optical, disk-shaped resonator. Combined with a technique called photothermal induced resonance (PTIR), which uses infrared light to examine a material’s composition, the incorporation of the resonator enables the probe to make high-precision measurements of minuscule, rapid changes in a material.
    Credit: NIST

    The achievement takes the AFM into a new realm, enabling the instrument to measure time-varying nanoscale processes that may change as quickly as ten billionths of a second. “This is truly a transformational advance,” said NIST scientist Andrea Centrone.

    Centrone, Vladimir Aksyuk, and their colleagues employed the new AFM capabilities in experiments using photothermal induced resonance (PTIR), a technique that combines the acuity of an AFM with the ability to determine the composition of materials using infrared light.

    With the new AFM-PTIR system, the scientists measured with high precision the rapid, but minute expansion of individual microcrystals heated by a light pulse. The microcrystals examined by the team belong to a class of materials known as metal-organic frameworks (MOFs). These materials contain nanosized pores that act as miniature sponges, which can store gas and serve as drug delivery containers, among other applications.

    Accurate knowledge of how well MOFs conduct heat is crucial for designing these materials for specific applications. However, most MOFs are microcrystals, which are too small for conventional instruments to measure their thermal conductivity. Instead, the team used the new AFM-PTIR system to record how long it took for the MOF crystals to cool down and return to their original size after they were heated by the light pulse and thermally expanded. The researchers then used that information to determine the thermal conductivity of individual MOF microcrystals, a feat that had never before been accomplished.

    The AFM system designed by Aksyuk and his colleagues features two key elements. First, the researchers shrunk and slimmed down the AFM’s probe, a small cantilever that acts like a spring, deflecting and vibrating when a sample exerts a force on it. Fashioned in the NanoFab at NIST’s Center for Nanoscale Science and Technology (CNST), the new probe weighs a mere trillionth of a gram. The minuscule mass enabled the probe to respond more quickly to a tiny force or displacement such as the one induced by the thermal expansion of the MOF the team examined.

    The researchers integrated the cantilever with a miniature disk-shaped waveguide that acts like an optical version of a whispering gallery. Just as a whispering gallery allows certain frequencies of sound waves to travel freely around a dome, the waveguide allows certain frequencies of light to resonate, circulating around the disk.

    The AFM cantilever and the disk are separated by a mere 150 nanometers. That’s close enough that tiny motions of the cantilever change the resonant frequencies in the disk, in effect transforming the small mechanical motion of the AFM probe into a large change in optical signal. Although scientists have combined optical cavities with other measuring tools, the team’s system is the first to integrate this kind of optical device in an AFM.

    Centrone, Aksyuk and their colleagues described the findings in a recent publication in Nano Letters .

    Aksyuk and his collaborators painstakingly designed, fabricated and tested the system using an array of nanofabrication tools at the CNST. The new AFM-PTIR system can record a displacement as small as a trillionth of a meter that occurs over a time scale as short as 10 billionths of a second. The team now plans to work on increasing the speed of the PTIR technique and using the probe to make measurements in water, a more suitable environment for examining biological samples.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    NIST Campus, Gaitherberg, MD, USA

    NIST Mission, Vision, Core Competencies, and Core Values

    NIST’s mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

     
  • richardmitnick 3:12 pm on July 13, 2017 Permalink | Reply
    Tags: , INFO-Integrated Near-Field Optoelectronic, , NIST, The probe tip also functions as a light source for measuring how a sample responds to illumination, The system uses gallium nitride (GaN) nanowires as the basis of the nanoprobe   

    From NIST: “Sub-microscopic LEDs Shed New Light on Advanced Materials” 

    NIST

    July 12, 2017
    Media Contact
    Ben Stein
    benjamin.stein@nist.gov
    (301) 975-2763

    Technical Contact
    Kris A. Bertness
    kris.bertness@nist.gov
    (303) 497-5069

    One of the persistent challenges in 21st century metrology is the need to measure ever-more-detailed properties of ever-smaller things, from microchip features to subcomponents of biological cells. That’s why, four years ago, a team of NIST scientists patented (link is external) the design for a nanoscale probe system that can simultaneously measure the shape, electrical characteristics, and optical response of sample regions a few tens of nanometers (nm, billionths of a meter) wide. 100 nm is about one-thousandth the width of a human hair.

    1
    Matt Brubaker (left) and Kris Bertness with the chamber in which nanowires are formed. No image credit.

    Now the researchers from NIST’s Physical Measurement Laboratory are closing in on a working prototype. The newest version of the device, which has a probe tip that functions as an ultra-tiny LED “spotlight,” holds great promise for identifying cancer-prone tissue, testing materials for improved solar cells, and providing a new way to put circuits on microchips, among other uses.

    The Integrated Near-Field Optoelectronic (INFO) system has the general configuration of an atomic force microscope (AFM), in which a probe tip on the end of a tiny cantilever beam passes a few nanometers over the surface of a sample, recording exact details of its morphology. But the metal-plated INFO probe also serves as a transmitter that projects microwaves into the sample as well as a receiving antenna that detects the altered microwaves coming back out. The nature of that alteration reveals electrical and chemical properties of the material.

    The system uses gallium nitride (GaN) nanowires as the basis of the nanoprobe. “In addition to being a semiconductor, gallium nitride is mechanically very strong,” says group leader Kris Bertness. “It’s a ceramic, kind of like a high-performance kitchen knife. It’s tough as nails.” As a result, the probe – a few hundred nanometers wide at the point and about 4 micrometers (millionths of a meter) long – doesn’t lose its sharpness, which is critical to performance.

    But GaN has another major advantage: It is the material widely used in light-emitting diodes (LEDs). So, in addition to serving as an AFM and microwave transmitter/receiver, the probe tip also functions as a light source for measuring how a sample responds to illumination.

    3
    This image shows the NIST logo made from glowing nanowire LEDs. While the color of the nanowires in the image looks blue, they are actually emitting in the ultraviolet with a wavelength of approximately 380 nm. The other two images, from a scanning electron microscope, show the overall structure of the nanowires.

    Recently, the team found a way to increase the light output of their probe 100-fold by experimenting with the placement and configuration of “n-type” silicon-doped GaN (which has an excess of free electrons) and “p-type” magnesium-doped GaN, which has a surplus of “holes” – areas where electrons are missing. When an electron and hole combine, they release energy in the form of light, as in LEDs. (See illustration.) Conversely, when light strikes the material in a solar cell, its absorbed energy separates electrons and holes, prompting a current to flow.

    “INFO will allow you to illuminate your sample with near-field resolution (tens of nanometers) and also see if the electrical properties of your sample at that exact same location have changed using the microwave sensing method,” Bertness says. “That’s important, for example, in investigating solar cell materials. With this probe, you can see very locally how that conductivity changes when you illuminate it. Similarly, people are working on photodetectors that are based on polycrystalline materials. They would like to know how the grain boundaries differ in their response to light.”

    Integrated circuit fabricators could use INFO to look for defects and identify the exact location of specific dopant areas in ultra-small features. “The channels are now getting so small, about 15 nm or smaller, that where the dopant atoms actually sit matters,” Bertness says. “Nobody used to have to care about that, but now they might be able to sense those locations because you could optically excite the carriers in and out of the dopant atoms and sense the change with the microwave reflection.

    “Another benefit is that the near-ultraviolet light from the probe tip is very tightly focused, so it can also be used to do much higher resolution lithography than you can do in your standard clean room. In conventional lithography, a beam is directed down at the material surface and directed onto specific exposure areas by using a mask. The INFO probe, however, can use a process called ‘direct write’ that doesn’t require a mask. You could program your probe to move in a specific pattern and coordinate that motion with when the light comes on and off, and you would expose just what you needed.”

    There are numerous potential biological applications. For example, there is some evidence that the mechanical stiffness of collagen – the ubiquitous protein that provides support for all parts of the body – may be related to whether cancer cells are more likely to recur or metastasize. “What medical researchers do now is use AFMs to go in and measure the stiffness of tissue,” Bertness says. “But while they’re doing that, they have no way of knowing when the probe is on collagen or something else. INFO might be able to help. Collagen has very interesting, unique optical properties. So, if scientists could illuminate the sample at the same time they’re doing stiffness measurements, they could determine what kind of tissue the probe is over.”

    Increasing the LED light output from the probe required a prolonged research effort involving the development of several key capabilities. One of the most difficult problems was developing selective-area nanowire growth, which is a process through which nanowire growth can be prescribed at specified locations. Identification and control over the crystal polarity that develops as the GaN wires grow was found to be critical in developing this capability. Another was determining the right geometry and formation conditions for the p-type section of the probe.

    “Initially we tried to fabricate the p-type section as an axial extension of the nanowire probe, however the high-temperature growth conditions required for this type of structure precluded effective p-type doping. In principle, a better p-section could be obtained at lower growth temperatures, however an increased radial growth rate caused nanowires to merge together in our LED test samples,” says project scientist Matt Brubaker. “By synthesizing isolated nanowires via selective area nanowire growth, we could avoid the merging issue and use radial growth to our advantage in synthesizing a core-shell geometry.” After achieving the 100-fold increase in light intensity, “we want to start making these probes and applying them,” Bertness says. “We need to do demonstrations and get some publications out there. That will help us look for potential researchers who could benefit from this technology.”

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    NIST Campus, Gaitherberg, MD, USA

    NIST Mission, Vision, Core Competencies, and Core Values

    NIST’s mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

     
  • richardmitnick 9:51 am on July 2, 2017 Permalink | Reply
    Tags: , MEMS - microelectromechanical systems technologies, NIST   

    From NIST: “Intrinsic Properties: The Secret Lives of Accelerometers” 

    NIST

    May 30, 2017

    Media Contact
    Ben Stein
    benjamin.stein@nist.gov
    (301) 975-2763

    Technical Contact
    Michael Gaitan
    michael.gaitan@nist.gov
    (301) 975-2070

    1
    http://www.industrial-electronics.com/DAQ/industrial_electronics/input_devices_sensors_transducers_transmitters_measurement/Accelerometers.html

    Accelerometers — devices that measure change in velocity — are built into automobiles, airplanes, cell phones, pacemakers, and scores of other products. They warn of potentially destructive vibration in industrial equipment, buildings, and bridges; register seismic shocks; and guide missiles to their targets.

    Increasingly, they are miniaturized using microelectromechanical systems (MEMS) technologies with component dimensions on the order of micrometers, and simultaneously register acceleration in all three axes of three-dimensional space. Because errors are additive when calculating velocity from acceleration, even minor errors in output can have very serious consequences.

    Yet when three-axis sensitivities and cross-axis sensitivities of a digital three-axis* device are tested at different calibration laboratories, the measurements can vary substantially depending on factors that can be difficult to determine, but often arise from errors with alignment of the test equipment, the internal alignment of the accelerometers in the device, or both.

    Now NIST scientists have devised a methodology designed to reduce or eliminate those differences by characterizing intrinsic properties of an accelerometer – those that are unique to it irrespective of the way it is mounted or tested — thus making possible accurate interlaboratory comparisons.

    “Determination of intrinsic properties is part of NIST’s larger effort to help industry develop standard testing protocols for the new MEMS-based device technologies, which do not exist at present,” says Michael Gaitan of NIST’s Physical Measurement Laboratory, which is working in partnership with the MEMS and Sensors Industry Group (MSIG) and the Institute of Electrical and Electronics Engineers. “Testing was reported by MSIG to be as much as half the cost of manufacturing for these sorts of devices. Manufacturers can’t reduce the cost of physical fabrication very much. But they can find savings in the way they package, test, and calibrate the devices.”

    When MEMS-based, three-axis accelerometers are tested, they are typically mounted on a gimbal system and rotated about three axes — x, y, and z — with measurements taken in different orientations. The measurements are formatted in a three-by-three grid, called a “cross-sensitivity matrix,” used by manufacturers to evaluate device performance. It specifies the relation between the acceleration response along the gimbal axes to the response along the axes of the device under test (DUT).

    That process, however, assumes that the DUT’s three axes are perfectly orthogonal – at right angles to each other – and that the device has been mounted in perfect alignment with the gimbal axes, which are themselves perfectly aligned. And in the case of testing accelerometer packages after they have been integrated into products, such as smart phones, it assumes that the package was installed in exact alignment with the axes of the phone case. But none of those conditions is guaranteed, and slight deviations in any of the variables can explain why measurements of the same test unit made at different laboratories produce different values.

    “So instead of using the cross-sensitivity matrix alone,” Gaitan says, “we’re defining the device as having intrinsic properties in which the axes of the device are not assumed to be completely orthogonal. There might be some variation in their alignment.”

    In NIST’s measurement protocol, the DUT is mounted on the position and rate table which very accurately rotates the device in specific gradations through 360 degrees on each of the gimbal’s three axes while measuring the device response at each interval. The protocol reveals the DUT’s internal axis alignment, the magnitude of response of each axis in different orientations, and its “signal offset” – the constant amount by which measured readings differ from the “true” value.

    With that information, a central standards laboratory such as NIST could fully characterize the intrinsic properties of one or more DUTs and distribute the devices to other labs, which would use them to compare results and determine, for example, whether readings were skewed because of instrument-related measurement errors.

    Earlier this year, NIST acquired a new position and rate table large enough to permit measurements on entire products that have accelerometers installed. “Our initial gimbal system was a smaller instrument that was useful for making static measurements,” Gaitan says.

    “But now we can make dynamic measurements on objects as large as a cell phone. We can set it to steady-state rotation like a record player, and we can accelerate the rotation rate. That will enable us to make measurements above the 1g acceleration of gravity and measure acceleration by rotation.”

    • Although it is called a “three-axis accelerometer,” the device in fact contains three separate accelerometers, each of which measures velocity change along one axis. Those signals are merged to register movement in three dimensions.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    NIST Campus, Gaitherberg, MD, USA

    NIST Mission, Vision, Core Competencies, and Core Values

    NIST’s mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

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

    From PTB: “The sharpest laser in the world” 

    PTB – The National Metrology Institute of Germany

    29.06.2017

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

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

    Address
    Physikalisch-Technische Bundesanstalt
    Bundesallee 100
    38116 Braunschweig

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

    See the full article here .

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

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

     
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