National Institute of Standards and Technology

About: National Institute of Standards and Technology is a government organization based out in Gaithersburg, Maryland, United States. It is known for research contribution in the topics: Laser & Scattering. The organization has 26667 authors who have published 60661 publications receiving 2215547 citations. The organization is also known as: National Bureau of Standards & NIST.

Virtual assembly using virtual reality techniques

Abstract: Virtual reality is a technology which is often regarded as a natural extension to 3D computer graphics with advanced input and output devices. This technology has only recently matured enough to warrant serious engineering applications. The integration of this new technology with software systems for engineering, design, and manufacturing will provide a new boost to the field of computer-aided engineering. One aspect of design and manufacturing which may be significantly affected by virtual reality is design for assembly. This paper presents a research effort aimed at creating a virtual assembly design environment.

Making optical atomic clocks more stable with 10-16-level laser stabilization

Abstract: Scientists demonstrate a cavity-stabilized laser system with a reduced thermal noise floor, exhibiting a fractional frequency instability of 2 × 10−16. They use this system as a stable optical source in an ytterbium optical lattice clock to resolve an ultranarrow 1 Hz linewidth for the 518 THz clock transition. Consistent measurements with a clock instability of 5 × 10−16/√τ are reported.

Electronic Authentication Guideline

Abstract: This recommendation provides technical guidelines for Federal agencies implementing electronic authentication and is not intended to constrain the development or use of standards outside of this purpose. The recommendation covers remote authentication of users (such as employees, contractors, or private individuals) interacting with government IT systems over open networks. It defines technical requirements for each of four levels of assurance in the areas of identity proofing, registration, tokens, management processes, authentication protocols and related assertions. This publication supersedes NIST SP 800-63-1.

Generation of Bright Phase-matched Circularly-polarized Extreme Ultraviolet High Harmonics

Abstract: Circularly-polarized extreme ultraviolet and X-ray radiation is useful for analysing the structural, electronic and magnetic properties of materials. To date, such radiation has only been available at large-scale X-ray facilities such as synchrotrons. Here, we demonstrate the first bright, phase-matched, extreme ultraviolet circularly-polarized high harmonics source. The harmonics are emitted when bi-chromatic counter-rotating circularly-polarized laser pulses field-ionize a gas in a hollowcore waveguide. We use this new light source for magnetic circular dichroism measurements at the M-shell absorption edges of Co. We show that phase-matching of circularly-polarized harmonics is unique and robust, producing a photon flux comparable to linearly polarized high harmonic sources. This work represents a critical advance towards the development of table-top systems for element-specific imaging and spectroscopy of multiple elements simultaneously in magnetic and other chiral media with very high spatial and temporal resolution.

Direct frequency comb spectroscopy in the extreme ultraviolet

Abstract: By coupling a high-power, high-repetition-rate near-infrared frequency comb to a femtosecond optical cavity, a frequency comb operating in the extreme-ultraviolet spectral range has been produced, by high harmonic generation, and provides high-resolution spectroscopy in this spectral region. Laser-based optical frequency combs, so called because they emit evenly spaced spectral lines, are used in precision spectroscopy and other applications requiring accurate measurements, such as atomic clocks. Efforts to extend this capability to shorter wavelengths in the extreme ultraviolet — which would open up exciting new applications, including searches for variation in fundamental constants — have lacked sufficient power for the purpose until now. Jun Ye and co-workers demonstrate a new approach, using a high-power, high-repetition pulsed infrared laser coupled into an optical cavity, to produce an improved extreme UV comb. In a first precision spectroscopy demonstration, they use direct frequency comb spectroscopy to determine argon and neon atomic transitions with ultra-high precision. The development of the optical frequency comb (a spectrum consisting of a series of evenly spaced lines) has revolutionized metrology and precision spectroscopy owing to its ability to provide a precise and direct link between microwave and optical frequencies1,2. A further advance in frequency comb technology is the generation of frequency combs in the extreme-ultraviolet spectral range by means of high-harmonic generation in a femtosecond enhancement cavity3,4. Until now, combs produced by this method have lacked sufficient power for applications, a drawback that has also hampered efforts to observe phase coherence of the high-repetition-rate pulse train produced by high-harmonic generation, which is an extremely nonlinear process. Here we report the generation of extreme-ultraviolet frequency combs, reaching wavelengths of 40 nanometres, by coupling a high-power near-infrared frequency comb5 to a robust femtosecond enhancement cavity. These combs are powerful enough for us to observe single-photon spectroscopy signals for both an argon transition at 82 nanometres and a neon transition at 63 nanometres, thus confirming the combs’ coherence in the extreme ultraviolet. The absolute frequency of the argon transition has been determined by direct frequency comb spectroscopy. The resolved ten-megahertz linewidth of the transition, which is limited by the temperature of the argon atoms, is unprecedented in this spectral region and places a stringent upper limit on the linewidth of individual comb teeth. Owing to the lack of continuous-wave lasers, extreme-ultraviolet frequency combs are at present the only promising route to extending ultrahigh-precision spectroscopy to the spectral region below 100 nanometres. At such wavelengths there is a wide range of applications, including the spectroscopy of electronic transitions in molecules6, experimental tests of bound-state and many-body quantum electrodynamics in singly ionized helium and neutral helium7,8,9, the development of next-generation ‘nuclear’ clocks10,11,12 and searches for variation of fundamental constants13 using the enhanced sensitivity of highly charged ions14.