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We present a standalone dual-comb platform based on two mutually stable waveguide lasers integrated in the same glass chip. Residual fluctuations are compensated using an algorithm seeded only by interferograms, which yields transform-limited spectra.
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 present a short-delay fiber interferometer that employs a 90° optical hybrid to perform in-phase and quadrature detection. This instrument allows a passive and robust characterization of the frequency noise of highly stable laser oscillators.
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.
The lowest measured phase noise floors of photonically generated microwave signals are orders-of-magnitude above the quantum limit. We show this discrepancy is likely due to photocarrier scattering in high speed, high linearity photodetectors.
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.
A 100 MHz mode-locked laser is tuned unevenly over 325 kHz with a stepper motor to produce high-SNR spectroscopic measurements of HCN with a 3 GHz spectral resolution. A setup to reduce the resulting heterodyne bandwidth is also demonstrated.
We propose and demonstrate simple and robust techniques for improving the signal-to-noise ratio of heterodyne beats between a frequency comb and a continuous wave laser beyond the shot-noise limit of a single comb mode.
We demonstrate a method to compare optical clocks approaching 10−17 uncertainties through the exchange of optical pulses from phase-locked frequency combs. We discuss results over a 120 m air path and prospects for longer distances.
We demonstrate a free-space link for clock comparisons based on the two-way exchange of pulse trains from combs. The residual uncertainty is 5 × 10−17 in 100 seconds over a 120 m air path, with longer distances possible.
A detailed analysis of the behavior of a DFB fiber laser based on a high-speed tunable intra-cavity phase-shifter is presented. The phase-shifter made of a specially designed shape memory alloy is inducing a birefringence, thus allowing the laser to operate on either x or y polarization mode in the CW regime or in the -switched regime. The spectral characteristics of the laser are analyzed in detail...
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