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Publications

Search Publications by William C. Swann

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Displaying 1 - 25 of 151

Measurement of the 27Al+ and 87Sr absolute optical frequencies

January 21, 2021
Author(s)
Holly Leopardi, Kyle Beloy, Tobias B. Bothwell, Samuel M. Brewer, Sarah L. Bromley, Jwo-Sy Chen, Scott Diddams, Robert J. Fasano, Youssef S. Hassan, David B. Hume, Dhruv Kedar, Colin J. Kennedy, Isaac H. Khader, David R. Leibrandt, Andrew D. Ludlow, William F. McGrew, William R. Milner, Daniele Nicolodi, Eric Oelker, Thomas E. Parker, John M. Robinson, Stefania Romisch, Jeffrey A. Sherman, Lindsay I. Sonderhouse, William C. Swann, Jian Yao, Jun Ye, Xiaogang Zhang, Tara M. Fortier
We perform absolute measurement of the 27Al+ single-ion and 87Sr neutral lattice clock frequencies at the National Institute of Standards and Technology and JILA at the University of Colorado against a global ensemble of primary frequency standards. Over

Femtosecond Time Synchronization of Optical Clocks Off a Flying Quadcopter

April 18, 2019
Author(s)
Hugo Bergeron, Laura C. Sinclair, William C. Swann, Isaac H. Khader, Kevin C. Cossel, Michael A. Cermak, Jean-Daniel Deschenes, Nathan R. Newbury
Optical clock networks promise advances in global navigation, time distribution, coherent sensing, relativity experiments, dark matter searches and other areas1–12. Such networks will need to compare and synchronize clocks over free-space optical links

Measurement of the impact of turbulence anisoplanatism on precision free-space optical time transfer

February 27, 2019
Author(s)
William C. Swann, Martha I. Bodine, Isaac H. Khader, Jean-Daniel Deschenes, Esther Baumann, Laura C. Sinclair, Nathan R. Newbury
Future highly precise free-space optical clock networks will require optically-based two-way time and frequency transfer links. As these networks extend over longer distances, they will include links between moving platforms, e.g. ground-to-air or ground

Femtosecond Optical Two-Way Time-Frequency Transfer in the Presence of Motion

February 22, 2019
Author(s)
Laura C. Sinclair, Hugo Bergeron, William C. Swann, Isaac H. Khader, Kevin C. Cossel, Michael A. Cermak, Nathan R. Newbury, Jean-Daniel Deschenes
Platform motion poses significant challenges to high-precision optical time and frequency transfer. We give a detailed description of these challenges and their solutions in comb-based optical two-way time and frequency transfer (O-TWTFT). Specifically, we

Time Synchronization over a Free-Space Optical Communication Channel

December 20, 2018
Author(s)
Isaac H. Khader, Laura C. Sinclair, William C. Swann, Hugo Bergeron, Nathan R. Newbury, Jean-Daniel Deschenes
Free space optical (FSO) communication channels are typically used to transmit high-speed data between sites over the air. Here we repurpose an FSO digital communication system and use it directly for two-way time transfer. We demonstrate real-time

Femtosecond timekeeping: slip-free optical clockwork for optical timescales

April 3, 2018
Author(s)
Daniel I. Herman, Stefan Droste, Esther Baumann, Jonathan Roslund, Dmitriy Churin, Arman Cingoz, Jean-Daniel Deschenes, Isaac H. Khader, William C. Swann, Craig W. Nelson, Nathan R. Newbury, Ian R. Coddington
The generation of true optical time standards will require the conversion of the highly stable optical frequency output of an optical atomic clock to a high-fidelity time output. We demonstrate comb-based clockwork that phase-coherently integrates ~7x10e20

High temperature performance of the HITEMP2010 and HITRAN Online databases: comparison with frequency comb measurements of water vapor absorption from 6800 cm-1 to 7200 cm-1

April 3, 2018
Author(s)
Paul J. Schroeder, D Pfotenhauer, J Yang, William C. Swann, Ian R. Coddington, Nathan R. Newbury, Greg B. Rieker
The HITEMP2010 and HITRAN Online databases are important tools for predicting molecular absorption under various environmental conditions. At room temperature the databases can be quite accurate, owing to their development using room temperature absorption

Low-Loss Reciprocal Optical Terminals for Two-Way Time-Frequency Transfer

November 22, 2017
Author(s)
William C. Swann, Laura C. Sinclair, Isaac H. Khader, Nathan R. Newbury, Jean-Daniel Deschenes, Hugo Bergeron
Optical two-way time-frequency transfer (O-TWTFT) over atmospheric free-space paths requires low- loss, single-mode, bi-directional and fully reciprocal optical terminals for transmitting precise frequency comb pulses over 10 kilometer scale paths. We

Broadband, high-resolution investigation of advanced absorption lineshapes at high temperature

August 23, 2017
Author(s)
Ian R. Coddington, William C. Swann, Nathan R. Newbury, Paul J. Schroeder, Matthew J. Cich, Jinyu Yang, Brian J. Drouin, Gregory B. Rieker
Spectroscopic studies of planetary atmospheres and high-temperature processes (e.g. combustion) require absorption lineshape models that are accurate over extended temperature ranges. To date, advanced lineshapes, like the speed-dependent Voigt and Rautian

Open-path dual-comb spectroscopy to an airborne retroreflector

July 20, 2017
Author(s)
Kevin C. Cossel, Eleanor M. Waxman, Fabrizio R. Giorgetta, Michael A. Cermak, Dan Hesselius, Shalom Ruben, William C. Swann, Gregory B. Rieker, Nathan R. Newbury
We demonstrate a new technique for spatial mapping of multiple atmospheric gas species. This system is based on high-precision dual-comb spectroscopy to a retroreflector mounted on a flying multicopter. We measure the atmospheric absorption over long open

Fully-Stabilized All Polarization-Maintaining Fiber Erbium Frequency Comb

May 3, 2017
Author(s)
Laura C. Sinclair, Ian R. Coddington, William C. Swann, Kana Iwakuni, Nathan R. Newbury
We demonstrate a completely polarization-maintaining fiber frequency comb operating at a 200 MHz repetition rate and show stability and noise performance consistent with precision measurement applications. This design is compatible with a robust, fieldable

Synchronization of clocks through 12km of strongly turbulent air over a city

October 11, 2016
Author(s)
Laura C. Sinclair, William C. Swann, Hugo Bergeron, Esther Baumann, Michael A. Cermak, Ian R. Coddington, Jean-Daniel Deschenes, Fabrizio R. Giorgetta, Juan Juarez, Isaac H. Khader, Keith G. Petrillo, Katherine T. Souza, Michael L. Dennis, Nathan R. Newbury
We demonstrate real-time, femtosecond-level clock synchronization across a low-lying, strongly turbulent, 12-km horizontal air path by optical two-way time transfer. For this long horizontal free-space path, the integrated turbulence extends well into the

Tight real-time synchronization of a microwave clock to an optical clock across a turbulent air path

April 15, 2016
Author(s)
Hugo Bergeron, Laura C. Sinclair, William C. Swann, Craig W. Nelson, Jean-Daniel Deschenes, Esther Baumann, Fabrizio R. Giorgetta, Ian R. Coddington, Nathan R. Newbury
The ability to distribute the precise time and frequency from an optical clock to remote platforms could enable future precise navigation and sensing systems. Here we demonstrate tight, real-time synchronization of a remote microwave clock to a master

Dual-comb spectroscopy

April 14, 2016
Author(s)
Ian R. Coddington, Nathan R. Newbury, William C. Swann
Dual-comb spectroscopy is an emerging new spectroscopic tool that exploits the frequency resolution, frequency accuracy, broad bandwidth, and brightness of frequency combs for ultra-high resolution, sensitive broadband spectroscopy. By use of two coherent

Optical system design for femtosecond-level synchronization of clocks

February 13, 2016
Author(s)
Laura C. Sinclair, William C. Swann, Jean-Daniel Deschenes, Hugo Bergeron, Fabrizio R. Giorgetta, Esther Baumann, Michael A. Cermak, Ian R. Coddington, Nathan R. Newbury
Synchronization of optical clocks via optical two-way time-frequency transfer across free-space links can result in time offsets between the two clocks below tens of femtoseconds over many hours. The complex optical system necessary to support such

Femtosecond synchronization of optical clocks over free-space links

December 11, 2015
Author(s)
Jean-Daniel Deschenes, Laura C. Sinclair, Fabrizio R. Giorgetta, William C. Swann, Esther Baumann, Hugo Bergeron, Michael A. Cermak, Nathan R. Newbury
The use of optical clocks/oscillators in future ultra-precise navigation, gravitational sensing, and relativity experiments will require time comparison and synchronization over terrestrial or satellite free-space links. Here we demonstrate full

Broadband phase spectroscopy over turbulent air paths

September 4, 2015
Author(s)
Fabrizio R. Giorgetta, Greg B. Rieker, Esther Baumann, William C. Swann, Laura C. Sinclair, Jonathan Kofler, Ian R. Coddington, Nathan R. Newbury
Broadband atmospheric phase spectra are measured at sub-milliradian uncertainty corresponding to a 10-13 refractive index change, despite strong decoherence from atmospheric turbulence. A phase-sensitive dual-comb spectrometer acquires spectra over 233 cm

A compact optically coherent fiber frequency comb

August 18, 2015
Author(s)
Laura C. Sinclair, Jean-Daniel Deschenes, Lindsay I. Sonderhouse, William C. Swann, Isaac H. Khader, Esther Baumann, Nathan R. Newbury, Ian R. Coddington
We describe design and operation of a robust self-referenced, optically coherent frequency comb. The system robustness is derived from a combination of an optics package based on polarization-maintaining fiber, high signal-to-noise ratio (SNR) detection of

Frequency-Comb-Based Remote Sensing of Greenhouse Gases over Kilometer Air Paths

October 29, 2014
Author(s)
Greg B. Rieker, Fabrizio R. Giorgetta, William C. Swann, Jonathan Kofler, Alexander M. Zolot, Laura C. Sinclair, Esther Baumann, Christopher L. Cromer, G. Petron, Colm Sweeney, P P. Tans, Ian R. Coddington, Nathan R. Newbury
We demonstrate frequency comb tooth-by-tooth measurements of atmospheric gas absorption across a 2-km, turbulent, open-air path through coherent dual-comb spectroscopy. High accuracy, high signal-to-noise transmission spectra are acquired spanning 5990 to

Comb-calibrated laser ranging for three-dimensional surface profiling with micrometer-level precision at a distance

October 6, 2014
Author(s)
Esther Baumann, Fabrizio R. Giorgetta, Jean-Daniel Deschenes, William C. Swann, Ian R. Coddington, Nathan R. Newbury
Non-contact surface mapping at a distance is interesting in diverse applications including industrial metrology, manufacturing, forensics, and artifact documentation and preservation. Frequency modulated continuous wave (FMCW) laser detection and ranging

Precision limitations in coherent laser ranging due to speckle phase noise

August 15, 2014
Author(s)
Esther Baumann, Jean-Daniel Deschenes, Fabrizio R. Giorgetta, William C. Swann, Ian R. Coddington, Nathan R. Newbury
The ultimate precision of coherent laser three-dimensional mapping of a diffusely scattering surface will be determined by speckle noise. Speckle phase noise gives rise both to apparent range outliers and to excess range noise during lateral scans

Speckle phase noise in coherent laser ranging: fundamental precision limitations

August 8, 2014
Author(s)
Esther Baumann, Jean-Daniel Deschenes, Fabrizio R. Giorgetta, William C. Swann, Ian R. Coddington, Nathan R. Newbury
Frequency-modulated continuous-wave laser detection and ranging (FMCW LADAR) measures the range to a surface through coherent detection of the backscattered light from a frequency-swept laser source. The ultimate limit to the range precision of FMCW LADAR