Coherent dual-comb interferometry with quasi-integer-ratio repetition rates.

We demonstrate a generalized method for dual-comb interferometry that involves the use of two frequency combs with quasi-integer-ratio repetition rates. We use a 16.67 MHz comb to probe an 80-cm-long ring cavity and a 100 MHz comb to asynchronously sample its impulse response. The resulting signal can be seen as six time-multiplexed independent interferograms. We perform a deconvolution of the photodetector's impulse response to prevent any crosstalk between these multiplexed data sets. The measurement is then demultiplexed and corrected with referencing signals. We obtain a measurement with a spectral point spacing of 16.67 MHz and a spectral SNR of 55 dB by averaging 15,000 interferograms, corresponding to a measurement time of 500 s. Compared to conventional dual-comb spectroscopy, this generalized technique allows to either reduce the spectral point spacing or the acquisition time by changing the repetition rate of only one of the combs.

Light field camera as a Fourier transform spectrometer sensor: instrument characterization and passive spectral ranging.

This paper presents a concept using field cameras in combination with Fourier transform spectrometers. The device can produce five-dimensional (position-angle-spectra) data cubes. This can lead to accurate measurements in both spectrum and distance and allows a thorough characterization of the interferometer, as well as adds passive ranging information to hyperspectral images. Shear and tilt fringes are simultaneously observed in a fixed optical path difference interferometer, and a passive spectral ranging demonstration is done in both absorption and emission for the 500-900 nm spectral bands.

Range-resolved vibrometry using a frequency comb in the OSCAT configuration.

Two methods for performing range-resolved vibrometry measurements using frequency combs are presented. A modified correction algorithm taking into account the differences from the typical dual comb spectroscopic technique is developed. Results are presented showing the recovery of a human voice sample and other sounds from different vibrating surfaces, including a diffuse wall and a glass slab. When multiple surfaces are present, range selection makes it possible to select the surface from which the vibration is demodulated.

Chemical detection with hyperspectral lidar using dual frequency combs.

High-resolution spectral lidar measurements using dual frequency combs as a source is presented. The technique enables the range-resolved measurement of fine spectral features, such as gas absorption lines, provided that a suitable scatterer is present in the scene. Measurements of HCN absorption lines at 20 meters are presented, with a water droplet cloud and a diffusely reflective surface as scatterers.

Fully referenced single-comb interferometry using optical sampling by laser-cavity tuning.

The correction of setup and laser instabilities in a single-comb interferometric measurement using optical sampling by laser-cavity tuning is investigated. A two-reference solution that allows full correction of the interferogram is presented. The technique is compared to a slightly simpler one-reference correction. For the one-reference case, all the subtleties involved in this partial correction and the dependence between the achievable measurement accuracy and the setup parameters are highlighted. The parameters considered are the comb bandwidth, the laser-frequency noise, the required spectral resolution, the cavity scan speed, and the length of the delay line. For both referencing approaches, experimental results using a fiber delay line of 10 km and a 100 MHz mode-locked laser with its repetition rate swept at 500 Hz are shown.

Referenced passive spectroscopy using dual frequency combs.

A referenced passive spectroscopy scheme using infrared frequency combs is presented. We perform a noise analysis and compare the results with a classical Fourier transform spectrometer. Experimental results are shown and great agreement with theory is obtained.

Experimental demonstration of ultrafast all-fiber high-order photonic temporal differentiators.

We propose and demonstrate what we believe to be a new, simple, and compact all-fiber design for arbitrary-order ultrafast optical temporal differentiation. The proposed design allows us to implement any desired differentiation order using a maximum of two concatenated fiber gratings, both operating in transmission. A single specially apodized chirped fiber Bragg grating is required for implementing any even-order differentiator, whereas the immediately next odd-order differentiator can be implemented by concatenating a long-period fiber-grating first-order differentiator. Besides its simplicity, this scheme provides an optimized energetic efficiency. We experimentally demonstrate a set of high-order all-optical time differentiators (up to the fourth order) capable of accurately processing arbitrary optical waveforms with picosecond time features.