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We present a method of frequency comb-based two-way time transfer that allows sub-femtosecond synchronization even during motion with velocities of up to 24 m/s. To test synchronization under motion, a Doppler simulator based on a mobile retroreflector was added at one end of a 4-km free-space link. Using this simulator and Doppler-tolerant algorithms we demonstrate a time deviation which reaches...
The continued remarkable advances in optical clocks and oscillators has led to a parallel strong development of optical clock networks [1]. Such networks have the potential to support a wide range of applications from basic time/frequency dissemination, to clock-based geodesy, to tests of general relativity [1]. To support optical clocks/oscillators at their highest accuracy and precision, these networks...
We develop a system to convert the high frequency accuracy of optical clocks to an optical timescale that outputs a 1 pulse per second (PPS) optical time signal at a defined reference plane.
We show tight synchronization of a 10-GHz microwave oscillator to an optical clock across a 4-km intermittent free-space link. The microwave clock remains synchronized to within tens of femtoseconds.
We demonstrate frequency comb based, robust, long-term conversion of optical frequency standards to an optical timescale that outputs a 1 pulse per second (PPS) optical time signal at a defined reference plane. This level of robustness is essential for time standards based on optical clocks.
The rapid advance in optical clocks and oscillators calls for similar advances in free-space frequency/time transfer. I will discuss our frequency-comb based system for coherent optical transfer of time and frequency over free-space links with femtosecond level stabilities and with robustness to atmospheric turbulence.
We demonstrate time synchronization of two optical oscillators across a turbulent 4-km free-space link. The time offset between oscillators is below 4 fs at minute timescales with less than 50 fs wander over 40 hours.
Dual optical frequency combs at 2.8–3.4 μm with powers >210 mW were produced with femtosecond fiber-lasers and difference frequency generation. Interferograms between the combs have been demonstrated as a step towards mid-infrared dual-comb spectroscopy.
Frequency combs provide a broadband, coherent, calibrated optical output in a single mode beam. We discuss three sensing applications that exploit this unique combination of properties: molecular spectroscopy, optical time-frequency transfer, and three-dimensional surface mapping.
Precision free-space time-frequency transfer could advance fields where present microwave-based transfer is inadequate. We demonstrate an optical free-space link with femtosecond timing deviation and residual instability below 10−18 at 1000 seconds.
Precision spectroscopy of trapped HfF + will be used to search for the permanent electric dipole moment of the electron (eEDM). Prior to this study, spectroscopic information necessary for state preparation, readout, and analysis of systematic errors was not available. We have developed a powerful technique for broadband, high-resolution survey spectroscopy of molecular ions that combines...
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