Ultraviolet astronomical spectrograph calibration with laser frequency combs from nanophotonic lithium niobate waveguides.

Astronomical precision spectroscopy underpins searches for life beyond Earth, direct observation of the expanding Universe and constraining the potential variability of physical constants on cosmological scales. Laser frequency combs can provide the required accurate and precise calibration to the astronomical spectrographs. For cosmological studies, extending the calibration with such astrocombs to the ultraviolet spectral range is desirable, however, strong material dispersion and large spectral separation from the established infrared laser oscillators have made this challenging.

Erratum to: Supercontinuum in integrated photonics: generation, applications, challenges and perspectives.

[This corrects the article DOI: 10.1515/nanoph-2022-0749.].

Supercontinuum in integrated photonics: generation, applications, challenges, and perspectives.

Frequency conversion in nonlinear materials is an extremely useful solution to the generation of new optical frequencies. Often, it is the only viable solution to realize light sources highly relevant for applications in science and industry. In particular, supercontinuum generation in waveguides, defined as the extreme spectral broadening of an input pulsed laser light, is a powerful technique to bridge distant spectral regions based on single-pass geometry, without requiring additional seed lasers or temporal synchronization.

Digital OPLL-based distributed Brillouin sensing system in optical fibers.

A digital optical phase-locked loop (OPLL) has been implemented to develop a distributed Brillouin sensing system in optical fibers. In our experiment, two commercial semiconductor lasers are phase-locked to each other with a highly flexible offset frequency using field programmable gate array (FPGA)-based electronics. Then, the difference frequency between the two lasers is highly stabilized and scanned by a desired step frequency in the vicinity of the Brillouin frequency of standard single-mode optical fibers.

Dual-comb cavity ring-down spectroscopy.

Cavity ring-down spectroscopy is a ubiquitous optical method used to study light-matter interactions with high resolution, sensitivity and accuracy. However, it has never been performed with the multiplexing advantages of direct frequency comb spectroscopy without significantly compromising spectral resolution. We present dual-comb cavity ring-down spectroscopy (DC-CRDS) based on the parallel heterodyne detection of ring-down signals with a local oscillator comb to yield absorption and dispersion spectra.