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Search Publications

NIST Authors in Bold

Displaying 32476 - 32500 of 73830

Improved Limits on Variation of the Fine Structure Constant and Violation of Local Position Invariance

May 29, 2007
Author(s)
Tara M. Fortier, Neil Ashby, James C. Bergquist, Marie Delaney, Scott A. Diddams, Thomas P. Heavner, Leo W. Hollberg, Wayne M. Itano, Steven R. Jefferts, K Kim, Windell Oskay, Thomas E. Parker, Jon H. Shirley, Jason Stalnaker, Filippo Levi, Luca Lorini
We report tests of Local Position Invariance (LPI) and constancy of fundamental constants from measurements of the frequency ratio of the 282-nm 199Hg + optical clock transition to the ground-state hyperfine splitting in 133Cs. Analysis of the frequency

Increased Cross-Correlation in Cascaded Four-Wave Mixing Processes

May 29, 2007
Author(s)
Jingyun Fan, Alan L. Migdall, L Wang
We report the measurement of increased noise cross-correlation between stokes and anti-stokes beams created in cascaded four-wave mixing processes with dual pump wavelengths, when two-photon light is efficiently created at the middle frequency. This method

Microwave Optoelectronic Oscillator with Optical Gain

May 29, 2007
Author(s)
Craig W. Nelson, Archita Hati, David A. Howe, W Zhou
Optoelectronic oscillators (OEO) are unique compared to radio-frequency (RF) oscillators in that they do not fundamentally require a RF gain element in order to satisfy the amplitude threshold condition for oscillation. All the energy required for

Microwave optoelectronic oscillator with optical gain

May 29, 2007
Author(s)
Craig Nelson, Archita Hati, David A. Howe, W Zhou
Optoelectronic oscillators (OEO) are unique compared to radio-frequency (RF) oscillators in that they do not fundamentally require a RF gain element in order to satisfy the amplitude threshold condition for oscillation. All the energy required for

Narrow band microwave radiation from a biased single-Cooper-pair transistor

May 29, 2007
Author(s)
Ofer Naaman, Joe Aumentado
We show that a single-Cooper-pair transistor (SCPT) electrometer emits narrow-band microwave radiation when biased in its sub-gap region. Photo-activation of quasiparticle tunneling in a nearby SCPT is used to spectroscopically detect this radiation, in a

Optical Fiber Vibration and Acceleration Model

May 29, 2007
Author(s)
Neil Ashby, David A. Howe, Jennifer A. Taylor, Archita Hati, Craig W. Nelson
We derive expressions for the group velocities of transverse electric and transverse magnetic electromagnetic waves in a stretched single-mode fiber. Stretching can occur either as a result of temperature changes of the spool on which the fiber is wound

Peak Deviation from Prediction in Atomic Clocks

May 29, 2007
Author(s)
Marc A. Weiss, A Masarie, Ron Beard
Results from a preliminary study of two GPS clocks tested on the ground show that the distribution of peak deviations from prediction cannot be assumed to be Gaussian. The standards are identical to models on board GPS block IIR satellites. The data were

Phase Noise of X-band Oscillator and Amplifier Technologies Compared

May 29, 2007
Author(s)
David A. Howe, Archita Hati
We compare best-in-class phase noise of different technologies of oscillators and amplifiers at X-band. Results are presented based on recent measurements at NIST. In particular, comparisons are made between mature technologies of multiplied quartz

Preliminary study on the vibration sensitivity performance of microwave components

May 29, 2007
Author(s)
Archita Hati, Craig W. Nelson, David A. Howe, Neil Ashby, Jennifer A. Taylor, Kai Hudek, C. Hay, David Seidel, D. Eliyahu
Vibration sensitivity is an important specification for oscillators on mobile systems, Unmanned Aerial Vehicles (UAVs) etc. These systems must provide superior performance when subject to severe environmental conditions. Electronic oscillators often can

Stable Laser System for Probing the Clock Transition at 578 nm in Neutral Ytterbium

May 29, 2007
Author(s)
Christopher W. Oates, Zeb Barber, Jason Stalnaker, C Hoyt, Tara M. Fortier, Scott A. Diddams, Leo W. Hollberg
In this paper we describe a new laser system we have developed to probe the ultra-narrow 1S 0 -> 3P 0 clock transition at 578 nm in neutral ytterbium. The yellow light is produced by sum frequency generation in a periodically-poled waveguide. With

Fiber laser-based frequency combs with high relative frequency stability

May 28, 2007
Author(s)
Nathan R. Newbury, William C. Swann, Ian R. Coddington, J. C. Bergquist, Scott Diddams, Luca Lorini
We describe our current low-noise fiber-laser frequency comb and present measurements of its residual instability. Through a comparison with a Ti:Sapphire frequency comb, we measure residual fractional frequency instabilities (Allan deviation) of 6x10 -17

Testing Local Position Invariance with Four H Masers AND Four Cs Fountains

May 28, 2007
Author(s)
Neil Ashby, Thomas P. Heavner, Steven R. Jefferts, A Radnaev, Y Dudin
We report the most sensitive tests to date of the assumption of local position invariance (LPI) underlying general relativity, based on a seven year comparison of cesium and hydrogen atomic clocks (frequency standards). The latest results place an upper

Numerical Optimization of Matrix-Assisted Laser Desorption/Ionization Time-of- Flight Mass Spectrometry: Application to Synthetic Polymer Molecular Mass Distribution Measurement

May 26, 2007
Author(s)
William E. Wallace, Charles M. Guttman, Kathleen M. Flynn, Anthony J. Kearsley
A novel approach is described for the selection of optimal instrument parameters that yield a mass spectrum which best replicates the molecular mass distribution of a synthetic polymer. The application of implicit filtering algorithms is shown to be a

AC-Mode SW-IR Radiation Thermometers for Measurement of Ambient Temperatures

May 25, 2007
Author(s)
George P. Eppeldauer, Howard W. Yoon
Recent improvements in the fabrication technology of short-wave infrared (SWIR) quantum detectors opened a new era in radiation thermometry. Ambient and higher temperatures can be measured with low uncertainties using thermoelectrically (TE) cooled

Cholesterol/Phospholipid Interactions in Hybrid Bilayer Membranes

May 25, 2007
Author(s)
Dustin Levy, Kimberly Briggman
The interactions between cholesterol and saturated phospholipids in hybrid bilayer membranes (HBMs) were investigated using the interface-sensitive technique of vibrational sum frequency spectroscopy (VSFS). The unique sensitivity of VSFS to order/disorder

Dielectric polarization evolution equations and relaxation times

May 25, 2007
Author(s)
James R. Baker-Jarvis, Billy F. Riddle, Michael D. Janezic
In this paper we develop a model that can describe broadband dielectric response, and includes frequency-dependent loss and the effects of the local electric field. The model is based on a correlation-function approach that we previously developed using

Polymer Viscoelasticity and Residual Stress Effects on Nanoimprint Lithography

May 24, 2007
Author(s)
Yifu Ding, Hyun Wook Ro, Jack F. Douglas, Ronald L. Jones, Daniel R. Hines, Alamgir Karim, Christopher L. Soles
We examine the influence of viscoelastic effects on the stability of nanoimprinted polymer films. The decay of features for polymers below the critical entanglement molecular mass at elevated temperatures is determined by simple surface tension and the
Displaying 32476 - 32500 of 73830
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