36 research outputs found
Laser time-transfer and space-time reference in orbit
A high performance Space-Time Reference in orbit could be realized using a
stable atomic clock in a precisely defined orbit and linking that to high
accuracy atomic clocks on the ground using a laser based time-transfer link.
This would enhance performance of existing systems and provide unique
capabilities in navigation, precise timing, earth sciences, geodesy and the
same approach could provide a platform for testing fundamental physics in
space. Precise laser time- and frequency-transfer from the ground to an
orbiting satellite would make it possible to improve upon the current state of
the art in timing (about 1 to 30 ns achieved with GPS) by roughly a factor of
1000 to the 1 ps level.Comment: Presented at the Sixth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, June 17-21, 201
Stable isotopic analysis of atmospheric methane by infrared spectroscopy by use of diode laser difference-frequency generation
An infrared absorption spectrometer has been constructed to measure the stable isotopic composition of atmospheric methane samples. The spectrometer employs periodically poled lithium niobate to generate 15 μW of tunable difference-frequency radiation from two near-infrared diode lasers that probe the ν3 rotational-vibrational band of methane at 3.4 μm. To enhance the signal, methane is extracted from 25 l of air by use of a cryogenic chromatographic column and is expanded into the multipass cell for analysis. A measurement precision of 12‰ is demonstrated for both δ13C and δD
Resonant interaction of trapped cold atoms with a magnetic cantilever tip
Magnetic resonance in an ensemble of laser-cooled trapped Rb atoms is excited
using a micro- cantilever with a magnetic tip. The cantilever is mounted on a
multi-layer chip designed to capture, cool, and magnetically transport cold
atoms. The coupling is observed by measuring the loss from a magnetic trap as
the oscillating cantilever induces Zeeman state transitions in the atoms.
Interfacing cold atoms with mechanical devices could enable probing and
manipulating atomic spins with nanometer spatial resolution and single-spin
sensitivity, leading to new capabilities in quantum computation, quantum
simulation, or precision sensing.Comment: 5 pages, 4 figure
Femtosecond frequency comb measurement of absolute frequencies and hyperfine coupling constants in cesium vapor
We report measurements of absolute transition frequencies and hyperfine
coupling constants for the 8S_{1/2}, 9S_{1/2}, 7D_{3/2}, and 7D_{5/2} states in
^{133}Cs vapor. The stepwise excitation through either the 6P_{1/2} or 6P_{3/2}
intermediate state is performed directly with broadband laser light from a
stabilized femtosecond laser optical-frequency comb. The laser beam is split,
counter-propagated and focused into a room-temperature Cs vapor cell. The
repetition rate of the frequency comb is scanned and we detect the fluorescence
on the 7P_{1/2,3/2} -> 6S_{1/2} branches of the decay of the excited states.
The excitations to the different states are isolated by the introduction of
narrow-bandwidth interference filters in the laser beam paths. Using a
nonlinear least-squares method we find measurements of transition frequencies
and hyperfine coupling constants that are in agreement with other recent
measurements for the 8S state and provide improvement by two orders of
magnitude over previously published results for the 9S and 7D states.Comment: 14 pages, 14 figure
Effect of atmospheric anisoplanatism on earth-to-satellite time transfer over laser communication links
© 2017 [2017 Optical Society of America.]. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited.The need for an accurate time reference on orbiting platforms motivates study of time transfer via free-space optical communication links. The impact of atmospheric turbulence on earth-to-satellite optical time transfer has not been fully characterized, however. We analyze limits to two-way laser time transfer accuracy posed by anisoplanatic non-reciprocity between uplink and downlink. We show that despite limited reciprocity, two- way time transfer can still achieve sub-picosecond accuracy in realistic propagation scenarios over a single satellite visibility period.Peer ReviewedPostprint (published version
Quenched narrow-line second- and third-stage laser cooling of 40Ca
We demonstrate three-dimensional (3-D) quenched narrow-line laser cooling and
trapping of 40Ca. With 5 ms of cooling time we can transfer 28 % of the atoms
from a magneto-optic trap based on the strong 423 nm cooling line to a trap
based on the narrow 657 nm clock transition (that is quenched by an
intercombination line at 552 nm), thereby reducing the atoms' temperature from
2 millikelvin to 10 microkelvin. This reduction in temperature should help
reduce the overall systematic frequency uncertainty for our Ca optical
frequency standard to < 1 Hz. Additional pulsed, quenched narrow-line
third-stage cooling in 1-D yields sub-recoil temperatures as low as 300 nK, and
makes possible the observation of high-contrast two-pulse Ramsey spectroscopic
lineshapes.Comment: 21 Pages including figures. Submitted to JOSA
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Delivery of High-Stability Optical and Microwave Frequency Standards over an Optical Fiber Network
Optical and radio frequency standards located in JILA and National Institute of Standards and Technology (NIST) laboratories have been connected through a 3.45-km optical fiber link. An optical frequency standard based on an iodine-stabilized Nd:YAG laser at 1064 nm (with an instability of ∼4×10−14 at 1 s) has been transferred from JILA to NIST and simultaneously measured in both laboratories. In parallel, a hydrogen maser-based radio frequency standard (with an instability of ∼2.4×10−13 at 1 s) is transferred from NIST to JILA. Comparison between these frequency standards is made possible by the use of femtosecond frequency combs in both laboratories. The degradation of the optical and rf standards that are due to the instability in the transmission channel has been measured. Active noise cancellation is demonstrated to improve the transfer stability of the fiber link
Optical Atomic Clock aboard an Earth-orbiting Space Station (OACESS): Enhancing searches for physics beyond the standard model in space
We present a concept for a high-precision optical atomic clock (OAC)
operating on an Earth-orbiting space station. This pathfinder science mission
will compare the space-based OAC with one or more ultra-stable terrestrial OACs
to search for space-time-dependent signatures of dark scalar fields that
manifest as anomalies in the relative frequencies of station-based and
ground-based clocks. This opens the possibility of probing models of new
physics that are inaccessible to purely ground-based OAC experiments such as
models where a dark scalar field is strongly screened near Earth's surface
Architecture for the photonic integration of an optical atomic clock
Laboratory optical atomic clocks achieve remarkable accuracy (now counted to 18 digits or more), opening possibilities to explore fundamental physics and enable new measurements. However, their size and use of bulk components prevent them from being more widely adopted in applications that require precision timing. By leveraging silicon-chip photonics for integration and to reduce component size and complexity, we demonstrate a compact optical-clock architecture. Here a semiconductor laser is stabilized to an optical transition in a microfabricated rubidium vapor cell, and a pair of interlocked Kerr-microresonator frequency combs provide fully coherent optical division of the clock laser to generate an electronic 22 GHz clock signal with a fractional frequency instability of one part in 10^(13). These results demonstrate key concepts of how to use silicon-chip devices in future portable and ultraprecise optical clocks