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Yet today's commercially available combs have a significant drawback. Because their tick marks are so finely spaced, the light output of these combs must be filtered to produce useful reference lines. This extra step adds complexity to the system and requires costly additional equipment. To resolve these kinds of issues, Caltech researchers looked to a kind of comb not previously deployed for astronomy. The novel comb produces easily resolvable lines, without any need for filtering. Furthermore, the Caltech comb is built from off-the-shelf components developed by the telecommunications industry. "We have demonstrated an alternative approach that is simple, reliable, and relatively inexpensive," says paper coauthor Kerry Vahala, the Ted and Ginger Jenkins Professor of Information Science and Technology and Applied Physics as well as the executive officer for Applied Physics and Materials Science in Caltech's Division of Engineering and Applied Science. The kind of frequency comb used by the researchers previously has been studied in the Vahala group in a different application, the generation of high-stability microwaves. "We believe members of the astronomical community could greatly benefit in their exoplanet hunting and characterization studies with this new laser frequency comb instrument," says Xu Yi, a graduate student in Vahala's lab and the lead author of a paper describing the work published in the January 27, 2016, issue of the journal Nature Communications. Scientists first began widely using laser frequency combs as precision rulers in the late 1990s in fields like metrology and spectroscopy; for their work, the technology's developers (John L. Hall of JILA and the National Institute of Standards and Technology (NIST) and Theodor Hänsch of the Max Planck Institute of Quantum Optics and Ludwig Maximilians University Munich) were awarded half of the Nobel Prize in Physics in 2005. In astronomy, the combs are starting to be utilized in the radial velocity, or "wobble" method, the earliest and among the most successful methods for identifying exoplanets. The "wobble" refers to the periodic changes in a star's motion, accompanied by starlight shifts owing to the Doppler effect, that are induced by the gravitational pull of an exoplanet orbiting around the star. The magnitude of the shift in the starlight's wavelength—on the order of quadrillionths of a meter—together with the period of the wobble can be used to determine an exoplanet's mass and orbital distance from its star. These details are critical for assessing habitability parameters such as surface temperature and the eccentricity of the exoplanet's orbit. With exoplanets that pass directly in front of (or "transit") their host star, allowing their radius to be determined directly, it is even possible to determine the bulk composition—for example, if the planet is built up primarily of gas, ice, or rock. In recent years, so-called mode-locked laser combs have proven useful in this task. These lasers generate a periodic stream of ultrashort light pulses to create the comb. With such combs, however, approximately 49 out of every 50 tick marks must be blocked out. This requires temperature- and vibration-insensitive filtering equipment. The new electro-optical comb that the Caltech team studied relies on microwave modulation of a continuous laser source, rather than a pulsed laser. It produces comb lines spaced by tens of gigahertz. These lines have from 10 to 100 times wider spacing than the tick marks of pulsed laser combs. To see how well a prototype would work in the field, the researchers took their comb to Mauna Kea in Hawaii. In September 2014, the instrument was tested at the NASA Infrared Telescope Facility (IRTF); in March 2015, it was tested with the Near Infrared Spectrometer on the W. M. Keck Observatory's Keck II telescope with the assistance of UCLA astronomer Mike Fitzgerald (BS '00) and UCLA graduate student Emily Martin, coauthors on the paper. The researchers found that their simplified comb (the entire electro-optical comb apparatus requires only half of the space available on a standard 19-inch instrumentation rack) provided steady calibration at room temperature for more than five days at IRTF. The comb also operated flawlessly during the second test—despite having been disassembled, stored for six months, and reassembled. "From a technological maturity point of view, the frequency comb we have developed is already basically ready to go and could be installed at many telescopes," says paper coauthor Scott Diddams of NIST. The Caltech comb produces spectral lines in the infrared, making it ideal for studying red dwarf stars, the most common stars in the Milky Way. Red dwarf stars are brightest in infrared wavelengths. Because red dwarfs are small, cool, and dim, planets orbiting these types of stars are easier to detect and analyze than those orbiting hotter sun-like stars. NASA's Kepler space observatory has shown that almost all red dwarf stars host planets in the range of one to four times the size of Earth, with up to 25 percent of these planets located in the temperate, or "habitable," zone around their host stars. Thus, many astronomers predict that red dwarfs provide the best chance for the first discovery of a world capable of supporting life. "Our goal is to make these laser frequency combs simple and sturdy enough that you can slap them onto every telescope, and you don't have to think about them anymore," says paper coauthor Charles Beichman, senior faculty associate in astronomy and the executive director of the NASA ExoPlanet Science Institute at Caltech. "Having these combs routinely available as a modest add-on to current and future instrumentation really will expand our ability to find potentially habitable planets, particularly around very cool red dwarf stars," he says. The research team is planning to double the frequency of the prototype comb's light output—now centered around 1,550 nanometers, in the infrared—to reach into the visible light range. Doing so would allow the comb also to calibrate spectra from sun-like stars, whose light output is at shorter, visible wavelengths, and thus seek out planets that are Earth's "twins." Other authors of the paper are Jiang Li, a visitor in applied physics and materials science, graduate students Peter Gao and Michael Bottom, and scientific research assistant Elise Furlan, all from Caltech; Stephanie Leifer, Jagmit Sandhu, Gautam Vasisht, and Pin Chen of JPL; Peter Plavchan (BS '01), formerly at Caltech and now a professor at Missouri State University; G. Ycas of NIST; Jonathan Gagne of the University of Montréal; and Greg Doppmann of the Keck Observatory. Explore further: Future 'comb on a chip': NIST's compact frequency comb could go places More information: X. Yi et al. Demonstration of a near-IR line-referenced electro-optical laser frequency comb for precision radial velocity measurements in astronomy, Nature Communications (2016). DOI: 10.1038/ncomms10436


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Damaging, deadly tornado clusters are becoming more common, a new study finds. Tornado clusters are outbreaks of twisters that span several days. One terrifying example is the April 25-28 outbreak in 2011, when some 350 tornadoes ripped across the south-central United States, killing more than 300 people. Outbreaks are responsible for 79 percent of tornado-related fatalities, said Michael Tippett, a climate and weather researcher at the School of Applied Science and Engineering and the Data Science Institute, both at Columbia University in New York. [Tornado Chasers: See Spinning Storms Up-Close (Photos)] Tippett's new research shows the number of tornadoes per outbreak is increasing. The analysis also discovered a 4-fold increase in the chance of extreme outbreaks — when hundreds of tornadoes spawn in storms. The researchers analyzed National Oceanic and Atmospheric Administration (NOAA) tornado records from 1954 to 2014. Outbreaks were counted when six or more EF-1 tornadoes started within 6 hours of each other, no matter the location. The scientists calculated the average number of tornadoes per outbreak, as well as variability— swings between high and low numbers of twisters — which relates to the chance of extreme outbreaks.. The findings were published Feb. 29 in the journal Nature Communications. The study was coauthored by Joel Cohen, a mathematical population biologist and head of the Laboratory of Populations at Rockefeller University in New York and Columbia's Earth Institute. "These discoveries suggest that the risks from tornado outbreaks are rising far faster than previously recognized," Cohen told Live Science in an email interview. The researchers analyzed National Oceanic and Atmospheric Administration (NOAA) tornado records from 1954 to 2014. Outbreaks were counted when six or more EF-1 tornadoes started within six hours of each other, no matter the location. They calculated the average tornadoes per outbreak, as well as variability — swings between high and low numbers of twisters. The total number of tornadoes (rated EF-1 and above) per year remained steady since the 1950s, the study reported. The Enhanced Fujita scale, or EF scale, ranks tornadoes based on wind speeds and damage. A tornado with wind speeds between 86 and 110 mph (138 and 177 km/h) is usually rated an EF-1. The highest rating is an EF-5. [See the Tornado Damage Scale in Images] However, the average number of tornadoes per outbreak rose from about 10 in the 1950s to about 15 in the past decade. The variability around that average rose four times faster. This statistical link, known as Taylor's power law, has been observed in other fields but never before with severe weather, Tippett told Live Science in an email interview. The new findings are consistent with several recent studies that suggest U.S. tornadoes are becoming more likely to strike in clusters. A NOAA study, published in October 2014 in the journal Science, showed a rise in the number of days with multiple reported tornadoes. Another study, published in July 2014 in the journal Climate Dynamics, found a similar clustering of tornadoes. The researchers said they can't blame climate change for the uptick in tornado outbreaks. However, the warming planet could be shifting weather patterns across the United States and triggering more tornadoes. For instance, extreme weather systems that spawn storms are now more likely to get stuck in one place for several days. Increasing warmth may also boost tornado outbreaks by sparking unstable weather earlier in the year. "We want to know what in the climate system is driving these changes. Some have implicated climate change. We think such a conclusion is premature, and further study is needed," Tippett said. Copyright 2016 LiveScience, a Purch company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.


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Site: http://phys.org/space-news/

"For the past 10 years, the NASA KOA team has boosted the science value of data acquired at Keck Observatory by providing the scientific community with open access to WMKO data," said Mario Perez, Keck Observatory Program Executive at NASA Headquarters in Washington. "They helped set a standard that all new ground based observatories are adopting. For this, the NASA KOA team has earned the NASA Group Achievement Award." "We are very proud of this award as well as the KOA project itself," said Hilton Lewis, Director of W. M. Keck Observatory. "This was the brainchild of Anne Kinney while she was at NASA and who I am happy to report recently joined Keck Observatory as our Chief Scientist. Thanks to her vision, data gathered by all instruments at Keck Observatory is available for everyone to use. The Keck Observatory telescopes are the most scientifically productive on Earth, responsible for gathering data used in about 300 peer-reviewed scientific papers per year – almost one per night. There are terabytes of valuable data collected over the last 20 years waiting to be mined." In 2004, NASA established a partnership with WMKO to acquire large volumes of data from a single instrument, the High Resolution Spectrograph (HIRES), for NASA science purposes. It is standard practice to make data from NASA's space telescopes available to the world in a public archive, but in 2004 it was unheard of to do the same with data from a ground-based telescope. Kinney, then Director of the Astrophysics Division at NASA Headquarters, decided to start a visionary project of promoting public access to these data, and the project began by archiving NASA-acquired HIRES data. In May 2005, Kinney signed the Keck Observatory Archive (KOA) agreement with her counterparts at the other institutions governing Keck Observatory: California Institute of Technology, the University of California, the University of Hawaii, the National Optical Astronomy Observatory, and the Jet Propulsion Laboratory. This partnership between NASA and Keck Observatory to make science data public was facilitated by the NASA Exoplanet Science Institute at Caltech. KOA immediately expanded to archive all HIRES data, not just NASA-acquired HIRES data. Next, by agreement of the partners, KOA expanded to include additional instruments at no significant increase in cost. Other facility instruments were included, and today all ten instruments that have acquired data over the lifetime of WMKO are part of KOA's holdings, including data acquired before the establishment of the KOA. The groundbreaking initiative of adopting standard practices of space archives to establish a permanent public archive of ground-based data has revolutionized the ground-based astronomical community and has been a model to other observatories to increase science productivity by establishing permanent public archives. The KOA pioneering achievements can be summarized as: The W. M. Keck Observatory operates the largest, most scientifically productive telescopes on Earth. The two, 10-meter optical/infrared telescopes near the summit of Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrographs and world-leading laser guide star adaptive optics systems.


Home > Press > New optical material offers unprecedented control of light and thermal radiation Abstract: Columbia Engineers discover that samarium nickelate shows promise for active photonic devices - SmNiO3 could potentially transform optoelectronic technologies, including smart windows, infrared camouflage, and optical communications. A team led by Nanfang Yu, assistant professor of applied physics at Columbia Engineering, has discovered a new phase-transition optical material and demonstrated novel devices that dynamically control light over a much broader wavelength range and with larger modulation amplitude than what has currently been possible. The team, including researchers from Purdue, Harvard, Drexel, and Brookhaven National Laboratory, found that samarium nickelate (SmNiO3) can be electrically tuned continuously between a transparent and an opaque state over an unprecedented broad range of spectrum from the blue in the visible (wavelength of 400 nm) to the thermal radiation spectrum in the mid-infrared (wavelength of a few tens of micrometers). The study, which is the first investigation of the optical properties of SmNiO3 and the first demonstration of the material in photonic device applications, is published online today in Advanced Materials. "The performance of SmNiO3 is record-breaking in terms of the magnitude and wavelength range of optical tuning," Yu says. "There is hardly any other material that offers such a combination of properties that are highly desirable for optoelectronic devices. The reversible tuning between the transparent and opaque states is based on electron doping at room temperature, and potentially very fast, which opens up a wide range of exciting applications, such as 'smart windows' for dynamic and complete control of sunlight, variable thermal emissivity coatings for infrared camouflage and radiative temperature control, optical modulators, and optical memory devices." Some of the potential new functions include using SmNiO3's capability in controlling thermal radiation to build "intelligent" coatings for infrared camouflage and thermoregulation. These coatings could make people and vehicles, for example, appear much colder than they actually are and thus indiscernible under a thermal camera at night. The coating could help reduce the large temperature gradients on a satellite by adjusting the relative thermal radiation from its bright and dark side with respect to the sun and thereby prolong the lifetime of the satellite. Because this phase-transition material can potentially switch between the transparent and opaque states with high speed, it may be used in modulators for free-space optical communication and optical radar and in optical memory devices. Researchers have long been trying to build active optical devices that can dynamically control light. These include Boeing 787 Dreamliner's "smart windows," which control (but not completely) the transmission of sunlight, rewritable DVD discs on which we can use a laser beam to write and erase data, and high-data-rate, long-distance fiber optic communications systems where information is "written" into light beams by optical modulators. Active optical devices are not more common in everyday life, however, because it has been so difficult to find advanced actively tunable optical materials, and to design proper device architectures that amplify the effects of such tunable materials. When Shriram Ramanathan, associate professor of materials science at Harvard, discovered SmNiO3's giant tunable electric resistivity at room temperature, Yu took note. The two met at the IEEE Photonics Conference in 2013 and decided to collaborate. Yu and his students, working with Ramanathan, who is a co-author of this paper, conducted initial optical studies of the phase-transition material, integrated the material into nanostructured designer optical interfaces--"metasurfaces"--and created prototype active optoelectronic devices, including optical modulators that control a beam of light, and variable emissivity coatings that control the efficiency of thermal radiation. "SmNiO3 is really an unusual material," says Zhaoyi Li, the paper's lead author and Yu's PhD student, "because it becomes electrically more insulating and optically more transparent as it is doped with more electrons--this is just the opposite of common materials such as semiconductors." It turns out that doped electrons "lock" into pairs with the electrons initially in the material, a quantum mechanical phenomenon called "strong electron correlation," and this effect makes these electrons unavailable to conduct electric current and absorbing light. So, after electron doping, SmNiO3 thin films that were originally opaque suddenly allow more than 70 percent of visible light and infrared radiation to transmit through. "One of our biggest challenges," Zhaoyi adds, "was to integrate SmNiO3 into optical devices. To address this challenge, we developed special nanofabrication techniques to pattern metasurface structures on SmNiO3 thin films. In addition, we carefully chose the device architecture and materials to ensure that the devices can sustain high temperature and pressure that are required in the fabrication process to activate SmNiO3." Yu and his collaborators plan next to run a systematic study to understand the basic science of the phase transition of SmNiO3 and to explore its technological applications. The team will investigate the intrinsic speed of phase transition and the number of phase-transition cycles the material can endure before it breaks down. They will also work on addressing technological problems, including synthesizing ultra-thin and smooth films of the material and developing nanofabrication techniques to integrate the material into novel flat optical devices. "This work is one crucial step towards realizing the major goal of my research lab, which is to make an optical interface a functional optical device," Yu notes. "We envision replacing bulky optical devices and components with 'flat optics' by utilizing strong interactions between light and two-dimensional structured materials to control light at will. The discovery of this phase-transition material and the successful integration of it into a flat device architecture are a major leap forward to realizing active flat optical devices not only with enhanced performance from the devices we are using today, but with completely new functionalities." Yu's team included Ramanathan, his Harvard PhD student You Zhou, and his Purdue postdoctoral fellow Zhen Zhang, who synthesized the phase-transition material and did some of the phase transition experiments (this work began at Harvard and continued when Ramanathan moved to Purdue); Drexel University Materials Science Professor Christopher Li, PhD student Hao Qi, and research scientist Qiwei Pan, who helped make solid-state devices by integrating SmNiO3 with novel solid polymer electrolytes; and Brookhaven National Laboratory staff scientists Ming Lu and Aaron Stein, who helped device nanofabrication. Yuan Yang, Assistant Professor of Materials Science and Engineering in the Department of Applied Physics and Applied Mathematics at Columbia Engineering, was consulted during the progress of this research. ### The study was funded by DARPA YFA (Defense Advanced Research Projects Agency Young Faculty Award), ONR YIP (Office of Naval Research Young Investigator Program), AFOSR MURI (Air Force Office of Scientific Research Multidisciplinary University Research Initiative) on metasurfaces, Army Research Office, and NSF EPMD (Electronics, Photonics, and Magnetic Devices) program. FUNDING: The work was supported by Defense Advanced Research Projects Agency Young Faculty Award (Grant No.D15AP00111), Office of Naval Research Young Investigator Award program (Grant No. N00014-16-1-2442), Air Force Office of Scientific Research (Grant No. FA9550-14-1-0389 through a Multidisciplinary University Research Initiative program, and Grant No. FA9550-12-1-0189), National Science Foundation (Grant No. ECCS-1307948), and Army Research Office (Grant Nos.W911NF-16-1-0042 and W911NF-14-1-0669). Research was carried out in part at the Center for Functional Nanomaterials, Brookhaven National Laboratory, which was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-SC0012704. The authors acknowledge helpful discussions with Yuan Yang, Assistant Professor of Materials Science and Engineering in the Department of Applied Physics and Applied Mathematics, Columbia Engineering. About Columbia University School of Engineering and Applied Science Columbia Engineering is one of the top engineering schools in the U.S. and one of the oldest in the nation. Based in New York City, the School offers programs to both undergraduate and graduate students who undertake a course of study leading to the bachelor's, master's, or doctoral degree in engineering and applied science. Columbia Engineering's nine departments offers 16 majors and more than 30 minors in engineering and the liberal arts, including an interdisciplinary minor in entrepreneurship with Columbia Business School. With facilities specifically designed and equipped to meet the laboratory and research needs of faculty and students, Columbia Engineering is home to a broad array of basic and advanced research installations, from the Columbia Nano Initiative and Data Science Institute to the Columbia Genome Center. These interdisciplinary centers in science and engineering, big data, nanoscience, and genomic research are leading the way in their respective fields while our engineers and scientists collaborate across the University to solve theoretical and practical problems in many other significant areas. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.


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PASADENA, CA — Promising new calibration tools, called laser frequency combs, could allow astronomers to take a major step in discovering and characterizing earthlike planets around other stars. These devices generate evenly spaced lines of light, much like the teeth on a comb for styling hair or the tick marks on a ruler — hence their nickname of "optical rulers." The tick marks serve as stable reference points when making precision measurements, such as those of the small shifts in starlight caused by planets pulling gravitationally on their parent stars. Yet today's commercially available combs have a significant drawback. Because their tick marks are so finely spaced, the light output of these combs must be filtered to produce useful reference lines. This extra step adds complexity to the system and requires costly additional equipment. To resolve these kinds of issues, Caltech researchers looked to a kind of comb not previously deployed for astronomy. The novel comb produces easily resolvable lines, without any need for filtering. Furthermore, the Caltech comb is built from off-the-shelf components developed by the telecommunications industry. "We have demonstrated an alternative approach that is simple, reliable and relatively inexpensive," says paper coauthor Kerry Vahala, the Ted and Ginger Jenkins Professor of Information Science and Technology and Applied Physics, as well as the executive officer for Applied Physics and Materials Science in Caltech's Division of Engineering and Applied Science. The kind of frequency comb used by the researchers previously has been studied in the Vahala group in a different application, the generation of high-stability microwaves. "We believe members of the astronomical community could greatly benefit in their exoplanet hunting and characterization studies with this new laser frequency comb instrument," says Xu Yi, a graduate student in Vahala's lab and the lead author of a paper describing the work published in the January 27, 2016, issue of the journal Nature Communications. Scientists first began widely using laser frequency combs as precision rulers in the late 1990s in fields like metrology and spectroscopy; for their work, the technology's developers (John L. Hall of JILA and the National Institute of Standards and Technology (NIST) and Theodor Hänsch of the Max Planck Institute of Quantum Optics and Ludwig Maximilians University Munich) were awarded half of the Nobel Prize in Physics in 2005. In astronomy, the combs are starting to be utilized in the radial velocity, or "wobble" method, the earliest and among the most successful methods for identifying exoplanets. The "wobble" refers to the periodic changes in a star's motion, accompanied by starlight shifts owing to the Doppler effect, that are induced by the gravitational pull of an exoplanet orbiting around the star. The magnitude of the shift in the starlight's wavelength — on the order of quadrillionths of a meter — together with the period of the wobble can be used to determine an exoplanet's mass and orbital distance from its star. These details are critical for assessing habitability parameters, such as surface temperature and the eccentricity of the exoplanet's orbit. With exoplanets that pass directly in front of (or "transit") their host star, allowing their radius to be determined directly, it is even possible to determine the bulk composition — for example, if the planet is built up primarily of gas, ice or rock. In recent years, so-called mode-locked laser combs have proven useful in this task. These lasers generate a periodic stream of ultrashort light pulses to create the comb. With such combs, however, approximately 49 out of every 50 tick marks must be blocked out. This requires temperature- and vibration-insensitive filtering equipment. The new electro-optical comb that the Caltech team studied relies on microwave modulation of a continuous laser source, rather than a pulsed laser. It produces comb lines spaced by tens of gigahertz. These lines have from 10 to 100 times wider spacing than the tick marks of pulsed laser combs. To see how well a prototype would work in the field, the researchers took their comb to Mauna Kea in Hawaii. In September 2014, the instrument was tested at the NASA Infrared Telescope Facility (IRTF); in March 2015, it was tested with the Near Infrared Spectrometer on the W. M. Keck Observatory's Keck II telescope with the assistance of UCLA astronomer Mike Fitzgerald (BS '00) and UCLA graduate student Emily Martin, coauthors on the paper. The researchers found that their simplified comb (the entire electro-optical comb apparatus requires only half of the space available on a standard 19-inch instrumentation rack) provided steady calibration at room temperature for more than five days at IRTF. The comb also operated flawlessly during the second test — despite having been disassembled, stored for six months, and reassembled. "From a technological maturity point of view, the frequency comb we have developed is already basically ready to go and could be installed at many telescopes," says paper coauthor Scott Diddams of NIST. The Caltech comb produces spectral lines in the infrared, making it ideal for studying red dwarf stars, the most common stars in the Milky Way. Red dwarf stars are brightest in infrared wavelengths. Because red dwarfs are small, cool and dim, planets orbiting these types of stars are easier to detect and analyze than those orbiting hotter sun-like stars. NASA's Kepler space observatory has shown that almost all red dwarf stars host planets in the range of one to four times the size of Earth, with up to 25 percent of these planets located in the temperate, or "habitable," zone around their host stars. Thus, many astronomers predict that red dwarfs provide the best chance for the first discovery of a world capable of supporting life. "Our goal is to make these laser frequency combs simple and sturdy enough that you can slap them onto every telescope, and you don't have to think about them anymore," says paper coauthor Charles Beichman, senior faculty associate in astronomy and the executive director of the NASA ExoPlanet Science Institute at Caltech. "Having these combs routinely available as a modest add-on to current and future instrumentation really will expand our ability to find potentially habitable planets, particularly around very cool red dwarf stars," he says. The research team is planning to double the frequency of the prototype comb's light output — now centered around 1,550 nanometers, in the infrared — to reach into the visible light range. Doing so would allow the comb also to calibrate spectra from sun-like stars, whose light output is at shorter, visible wavelengths and, thus, seek out planets that are Earth's "twins." Other authors of the paper are Jiang Li, a visitor in applied physics and materials science, graduate students Peter Gao and Michael Bottom, and scientific research assistant Elise Furlan, all from Caltech; Stephanie Leifer, Jagmit Sandhu, Gautam Vasisht, and Pin Chen of JPL; Peter Plavchan (BS '01), formerly at Caltech and now a professor at Missouri State University; G. Ycas of NIST; Jonathan Gagne of the University of Montréal; and Greg Doppmann of the Keck Observatory. The paper is titled "Demonstration of a near-IR line-referenced electro-optical laser frequency comb for precision radial velocity measurements in astronomy." The research performed at Caltech and JPL was funded through the President's and Director's Fund Program, and the work at NIST was funded by the National Science Foundation.

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