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We compare water-vapor absorption models generated with HITRAN Online and HITEMP2010 to measurements with a dual-comb spectrometer. For strong lines up to 1300K, HITRAN Online is a more accurate predictor of strengths, shapes, and positions.
Optical two-way time-frequency transfer (O-TWTFT) places stringent requirements on the free-space optical terminals used to transmit precise frequency comb pulses. We discuss a compact free-space terminal design that enables O-TWTFT over long, highly turbulent links.
We demonstrate dual-comb spectroscopy over a 11.6-km long urban open air path. The system provides time-resolved, high accuracy measurements of atmospheric transmission in the 1.6 micron atmospheric window for greenhouse gas quantification.
Near-infrared frequency-comb spectroscopy is a powerful tool with which to measure absorption of CO2, CH4, H2O over turbulent paths such as meter scale paths in active furnaces or 11 km horizontal paths over cities. Work of the U.S. government, not subject to copyright.
We demonstrate synchronization of two clocks to within femtoseconds across a 12 km air path over three days. We demonstrate adaptive-optics terminals can be used for improved link availability without degradation of the synchronization performance.
Near-infrared frequency-comb spectroscopy is used to measure CO2 absorption over a 2-km outdoor path under well-mixed atmospheric conditions. We compare integrated area, linecenter, and Lorentz widths extracted from Voigt fits to the data with HITRAN. Work of the U.S. government, not subject to copyright.
We discuss the design and performance of an all polarization-maintaining self-referenced frequency comb that can maintain optical coherence with an optical reference laser under strong vibrations from a shaker table and a moving vehicle.
Dual asynchronous comb techniques for precision measurement are coming of age. In spectroscopy such systems a can cover 42 THz of optical spectra with 100 MHz point spacing and signal to noise ratios (SNR) better than 3000. Careful examination of the systematic errors has begun and Doppler broadened molecular line centers can be determined reliably to within 200 kHz. In related systems dual and single...
Properly stabilized, frequency combs form high accuracy references across much of the optical spectrum. Here we employ dual frequency combs to harness this accuracy for fast and high resolution measurements of frequency agile CW lasers.
A coherent dual comb spectrometer spanning over 45 THz in the NIR was constructed from broadened erbium fiber lasers. Gas phase water, methane, and acetylene spectra were measured and characterized toward establishing absolute frequency references.
A femtosecond fiber laser with an intracavity electro-optic modulator is phase-locked to a high-finesse cavity through two cw transfer lasers. The residual phase noise at the 300 MHz harmonic is −126 dBc/Hz at 1 Hz. Work of the U.S.
Two coherent 1.5 μm frequency combs are transferred to 3.4 μm by difference-frequency generation with a 1064 nm cw laser. From a multi-heterodyne measurement, the residual linewidth between the comb teeth is resolution-limited at 200 mHz. Work of the U.S. government, not subject to copyright.
The time-resolved frequency spectrum of a frequency agile CW laser is measured with a 300 ms update rate and 3 kHz resolution/accuracy over a 28 nm wavelength range with a coherent dual comb setup.
Dual, coherent frequency combs are used to measure the spectrum of an incoherent, quasi-thermal source through Fourier spectroscopy. The source spectrum is acquired over 1 THz bandwidth with an absolute frequency accuracy set by the combs. Work of the U.S. government, not subject to copyright.
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