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Physics

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Displaying 801 - 825 of 2574

Enhanced observation time of magneto-optical traps using micro-machined non-evaporable getter pumps

October 6, 2020
Author(s)
Rodolphe Boudot, James P. McGilligan, Kaitlin R. Moore, Vincent N. Maurice, Gabriela Martinez, Azure L. Hansen, E. de Clercq, Elizabeth Donley, John Kitching
We show that micro-machined non-evaporable getter pumps (NEGs) can extend the time over which laser cooled atoms can be produced in a magneto-optical trap (MOT), in the absence of other vacuum pumping mechanisms. In a first study, we incorporate a silicon

Harnessing dispersion in soliton microcombs to mitigate thermal noise

October 5, 2020
Author(s)
Jordan Stone, Scott Papp
We explore intrinsic thermal noise in soliton microcombs, revealing thermodynamic correlations induced by nonlinearity and group-velocity dispersion. A suitable dispersion design gives rise to control over thermal-noise transduction from the environment to

Ultraprecise optical-frequency stabilization with heterogeneous III-V/Si lasers

September 15, 2020
Author(s)
Liron Stern, Wei Zhang, Lin Chang, Joel Guo, Chao Xiang, Minh A. Tran, Duanni Huang, Jon Peters, David Kinghorn, John E. Bowers, Scott Papp
Demand for low-noise, continuous-wave, frequency-tunable lasers based on semiconductor integrated photonics has been advancing in support of numerous applications. In particular, an important goal is to achieve narrow spectral linewidth, commensurate with

Protocol for Light-Shift Compensation in a Continuous-Wave Microcell Atomic Clock

September 8, 2020
Author(s)
Moustafa A. Hafiz, Remy Vicarini, Nicolas Passilly, Claudio Calosso, Vincent N. Maurice, Juniper Pollock, V Yudin, John Kitching, Rodolphe Boudot
Light shifts are known to be an important limitation to the mid- and long-term fractional frequency stability of different types of atomic clocks. In this article, we demonstrate the experimental implementation of an anti-light-shift interrogation protocol

The Next Generation of Current Measurement for Ionization Chambers

September 1, 2020
Author(s)
Ryan P. Fitzgerald, Denis E. Bergeron, Dean G. Jarrett, Neil M. Zimmerman, Carine Michotte, Hansjoerg Scherer, Stephen Giblin, Steven Judge
Re-entrant ionization chambers (ICs) are essential to radionuclide metrology and nuclear medicine for maintaining standards and measuring half-lives. Metrology-quality systems must be precise and stable to 0.1% over many years, and linear from 10^(-14) A

Synchronizing Stock Market Clocks to UTC(NIST)

August 29, 2020
Author(s)
Michael Lombardi
To reduce the possibility of fraudulent activity and market manipulation, the world's major stock exchanges require every clock involved in a stock market transaction to be synchronized to agree with a common reference clock that keeps accurate and

Position-dependent neutron detection efficiency loss in 3He gas proportional counters

August 22, 2020
Author(s)
Patrick N. Peplowski, Zachary W. Yokley, Madison Liebel, Shuo Cheng, Richard C. Elphic, Shannon Hoogerheide, David J. Lawrence, Jeffrey Nico
The position-dependent neutron detection response of a 3He gas proportional counter (GPC) was characterized using a collimated (3-mm-wide), monoenergetic 0.05 eV neutron beam. For neutrons incident on the GPC near the ends of the active region, the neutron

A miniaturized optical frequency standard for next generation portable optical clocks

August 7, 2020
Author(s)
Vincent N. Maurice, Zachary Newman, Susannah Dickerson, Morgan Rivers, Mark Mescher, John LeBlanc, John Kitching, Matthew Hummon, Cort Johnson
This paper describes the development and measurement of a miniaturized optical frequency standard based on the rubidium two-photon transition at 778 nm. The optical standard has been implemented on a micro-optics breadboard and operates on

General Methods for Suppressing the Light Shift in Atomic Clocks Using Power Modulation

August 3, 2020
Author(s)
V Yudin, M. Y. Basalaev, A. V. Taichenachev, Juniper Pollock, Zachary Newman, Moshe Shuker, Azure L. Hansen, Matthew Hummon, Elizabeth Donley, John Kitching
We show that the light shift in atomic clocks can be suppressed using time variation of the interrogation field intensity. By measuring the clock output at two intensity levels, error signals can be generated that simultaneously stabilize a local

Laser-cooling in a chip-scale platform

August 3, 2020
Author(s)
James P. McGilligan, Kaitlin R. Moore, Argyrios Dellis, Gabriela Martinez, E. de Clercq, Paul Griffin, A S. Arnold, E Riis, Rodolphe Boudot, John Kitching
Chip-scale atomic devices built around micro-fabricated alkali vapor cells are at the forefront of compact metrology and atomic sensors. We demonstrate a micro-fabricated vapor cell that is actively pumped to ultra-high-vacuum (UHV) to achieve laser

Does Cosmological Evolution Select for Technology?

July 30, 2020
Author(s)
Jeff Shainline
Fine tuning of the parameters defining the physics of our universe has been proposed to result from the natural selection of universes capable of prolific reproduction. This cosmic reproduction may occur through singularities, and it has been argued that

Understanding Photovoltaic Energy Losses under Indoor Lighting Conditions

July 28, 2020
Author(s)
Behrang H. Hamadani
The external luminescence quantum yield as a function of the solar cell current density when exposed to low indoor light was estimated based on absolute electroluminescence measurements and a self-consistent use of the electro-optical reciprocity

Nanophotonic tantala waveguides for supercontinuum generation pumped at 1560 nm

July 22, 2020
Author(s)
Kieran F. LaMee, David Carlson, Zachary Newman, Su P. Yu, Scott Papp
We experimentally demonstrate efficient and broadband supercontinuum generation in nonlinear tantala (Ta2O5) waveguides using a 1560 nm femtosecond seed laser. With incident pulse energies as low as 100 pJ, we create spectra spanning up to 1.6 octaves

Electromagnetics for Quantitative Magnetic Resonance Imaging

July 20, 2020
Author(s)
Stephen E. Russek, Karl F. Stupic, Joshua R. Biller, Michael A. Boss, Kathryn E. Keenan, Elizabeth Mirowski
Magnetic Resonance Imaging (MRI) is based on radio frequency (RF) interrogation of the human body at frequencies between 40 MHz to 300 MHz. An RF transmitter excites proton spin precession and then, in a manner analogous to an RF ID tag, the proton’s
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