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Physics

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Displaying 1051 - 1075 of 2516

Progress on Optical-clock-based Time Scale at NIST: Simulations and Preliminary Real-Data Analysis

April 20, 2018
Author(s)
Jian Yao, Jeffrey A. Sherman, Tara M. Fortier, Thomas E. Parker, Judah Levine, Joshua J. Savory, Stefania Romisch, William F. McGrew, Robert J. Fasano, Stefan A. Schaeffer, Kyle P. Beloy, Andrew D. Ludlow
This paper shows the recent NIST work on incorporating an optical clock into a time scale. We simulate a time scale composed of continuously-operating commercial hydrogen masers and an optical frequency standard that does not operate continuously as a

High harmonics with spatially varying ellipticity for spatially-resolved magnetic spectroscopy

April 17, 2018
Author(s)
Daniel D. Hickstein, Jennifer Ellis, Kevin M. Dorney, Nathan J. Brooks, Christian Gentry, Justin M. Shaw, Quynh Nguyen, Christopher A. Mancuso, Henry C. Kapteyn, Margaret M. Murnane, Carlos Hernandez-Garcia
In this work, we present a new method to produce ultrashort pulses of circularly polarized extreme ultraviolet light. We combine two orthogonally-polarized high-harmonic sources to produce a far-field beam with a uniform intensity distribution but with a

Photonic chip for laser stabilization to an atomic vapor at a precision of $10^{-11}$

April 11, 2018
Author(s)
Matthew T. Hummon, Songbai Kang, Douglas G. Bopp, Qing Li, Daron A. Westly, Sangsik Kim, Connor D. Fredrick, Scott A. Diddams, Kartik A. Srinivasan, John E. Kitching
We perform precision spectroscopy of rubidium confined in a micro-machined, 27~mm$^3$ volume, vapor cell using a collimated free space 120~$\bm{\mu}$m diameter laser beam derived directly from a single mode silicon nitride waveguide. With this optical

Mid-infrared frequency comb generation via cascaded quadratic nonlinearities in quasi-phase-matched waveguides

April 5, 2018
Author(s)
Abijith S. Kowligy, Alexander J. Lind, Daniel D. Hickstein, David R. Carlson, Henry R. Timmers, Nima Nader, Flavio Caldas da Cruz, Gabriel G. Ycas
We demonstrate mid-infrared (MIR) frequency comb generation in periodically poled lithium niobate (PPLN) waveguides pumped by nanojoule pulses from a 1.5 um mode-locked Er:fiber laser. The cascaded-c(2) nonlinearity in PPLN yields a nearly octave-spanning

Hyper-Ramsey spectroscopy with probe laser intensity fluctuations

March 29, 2018
Author(s)
Kyle P. Beloy
We examine the influence of probe laser intensity fluctuations on hyper-Ramsey spectroscopy. We assume, as is appropriate for relevant cases of interest, that the probe laser intensity $I$ determines both the Rabi frequency $(\propto\sqrt)$ and the

Incorporating an Optical Clock into a Time Scale at NIST: Simulations and Preliminary Real-Data Analysis

March 29, 2018
Author(s)
Jian Yao, Jeffrey A. Sherman, Tara M. Fortier, Thomas E. Parker, Judah Levine, Joshua J. Savory, Stefania Romisch, William F. McGrew, Robert J. Fasano, Stefan A. Schaeffer, Kyle P. Beloy, Andrew D. Ludlow
This paper shows the recent NIST work on incorporating an optical clock into a time scale. We simulate a time scale composed of continuously-operating commercial hydrogen masers and an optical frequency standard that does not operate continuously as a

SIM Time Scale: 10 years of operation

March 29, 2018
Author(s)
J. M. Lopez, Michael A. Lombardi, E. de Carlos, N. Munoz, C. Ortiz
The Inter-American Metrology System (SIM) is one of the world's five major Regional Metrology Organizations (RMO's). Starting in 2005, the SIM Time and Frequency Metrology Working Group (SIM TFWG) developed a time and frequency comparison network for the

Effects of resonant-laser excitation on the emission properties in a single quantum dot

March 27, 2018
Author(s)
Sergey Polyakov, Vivien Loo, Edward Flagg, Glenn S. Solomon, Olivier Gazzano, Tobias Huber
While many solid-state emitters can be optically excited non-resonantly, resonant excitation is necessary for many quantum information protocols as it often maximizes the non-classicality of the emitted light. Here, we study the resonance fluorescence in a

Topological lattice using multi-frequency radiation

March 19, 2018
Author(s)
Ian B. Spielman, Gediminas Juzeli?nas, Tomas Andrijauskas
We describe a novel technique for creating an artificial magnetic field for ultra-cold atoms using a periodically pulsed pair of counter propagating Raman lasers that drive transitions between a pair of internal atomic spin states: a multi-frequency

Reply to comment on "Relativistic Theory of the Falling Cube Gravimeter"

March 14, 2018
Author(s)
Neil Ashby
The comment\cite{kren17} claims that the paper Relativistic theory of the falling cube gravimeter \cite{ashby17} is incorrect. The authors of this comment assert that optical paths in the two interferometer arms of an absolute gravimeter shift only the

Millimeter-Wave Polarimeters Using Kinetic Inductance Detectors for TolTEC and Beyond

March 8, 2018
Author(s)
Jason Austermann, James A. Beall, Sean A. Bryan, Bradley Dober, Jiansong Gao, Gene C. Hilton, Johannes Hubmayr, Phillip Mauskopf, Christopher M. McKenney, S M. Simon, Joel Ullom, Michael Vissers, G W. Wilson
Microwave kinetic inductance detectors (MKIDs) provide a compelling path forward to the large-format polarimeter, imaging, and spectrometer arrays needed for next-generation experiments in millimeter-wave cosmology and astronomy. We describe the

Imaging catalytic CO2 reduction on Cu2O (110) -- A First-Principles study

March 5, 2018
Author(s)
Eric L. Shirley, John T. Vinson, Liang Li, Maria K. Chan, Jeffry Greeley, Jeffrey R. Guest, Rui Zhang
Balancing global energy needs against increasing greenhouse gas emissions requires new methods for efficient CO2 reduction. While photoreduction of CO2 is promising, the rational design of photocatalysts hinges on precise characterization of the surface

Optical-Frequency Measurements with a Kerr Microcomb and Photonic-Chip Supercontinuum

February 27, 2018
Author(s)
Erin S. Lamb, David R. Carlson, Daniel D. Hickstein, Jordan R. Stone, Scott A. Diddams, Scott B. Papp
Dissipative solitons formed in Kerr microresonators offer the promise of chip-scale frequency combs that can extend precision metrology outside of a laboratory environment. We explore the creation of an octave-spanning, 15 GHz repetition rate microcomb

NIST Time and Frequency Bulletin

February 23, 2018
Author(s)
Kathryn R. Stephenson
The Time and Frequency Bulletin provides information on performance of time scales and a variety of broadcasts (and related information) to users of the NIST services.

Weak and Strong Gels and the Emergence of the Amorphous Solid State

February 23, 2018
Author(s)
Jack F. Douglas
Gels are amorphous solids whose macroscopic viscoelastic response derives from contraints in the material that serve to localize the constituent molecules or particles about their average positions in space. These contraints may either be local in nature

Blade Coating Aligned, High-Performance, Semiconducting-Polymer Transistors

February 22, 2018
Author(s)
Lee J. Richter, Hyun W. Ro, Regis J. Kline, Daniel A. Fischer, Dean M. DeLongchamp, Lars Thomsen, Christopher McNeil, Dawei Wu, Maria Kaplan, Eliot H. Gann
Recent demonstration of mobilities in excess of 10 cm2V-1s-1 have energized research in solution deposition of polymers for thin film transistor applications. Due to the lamella motif of most soluble, semiconducting polymers, the local mobility is

Topological Rigidification of Flexible Polymers in Solution

February 22, 2018
Author(s)
Jack F. Douglas, Fernando Vargas-Lara
We use molecular dynamic simulations on a coarse-grained model for flexible polymers in solution to study how molecular topology affects the intrinsic rigidity of polymeric chains. In particular, we study how polymeric "topological complexity", defined by

What Does the Tg of Thin Polymer Films Really Tell Us?

February 22, 2018
Author(s)
Wengang Zhang, Francis W. Starr, Jack F. Douglas
The disparate results for Tg shifts in ultra-thin polymer films with the same film thickness, substrate, and chemistry raises the question of whether Tg is a useful way to characterize thin films. Underlying many Tg measurements is the assumption that Tg
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