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

TL;DR

This paper demonstrates the first use of ultraviolet laser frequency combs for calibrating astronomical spectrographs, enabling high-precision spectroscopy in the ultraviolet range crucial for cosmological research.

Contribution

It introduces a novel chip-integrated photonic approach using lithium niobate waveguides to generate ultraviolet astrocombs, overcoming previous material dispersion challenges.

Findings

Successful calibration of spectrographs in the ultraviolet below 400 nm

Implementation of chip-integrated nonlinear photonics for astrocombs

Potential to enhance astronomical spectroscopy precision

Abstract

Astronomical precision spectroscopy underpins searches for life beyond Earth, direct observation of the expanding Universe and constraining the potential variability of physical constants across cosmological scales. Laser frequency combs can provide the critically required accurate and precise calibration to the astronomical spectrographs. For cosmological studies, extending the calibration with such astrocombs to the ultraviolet spectral range is highly desirable, however, strong material dispersion and large spectral separation from the established infrared laser oscillators have made this exceedingly challenging. Here, we demonstrate for the first time astronomical spectrograph calibrations with an astrocomb in the ultraviolet spectral range below 400 nm. This is accomplished via chip-integrated highly nonlinear photonics in periodically-poled, nano-fabricated lithium niobate waveguides in conjunction with a robust infrared electro-optic comb generator, as well as a chip-integrated microresonator comb. These results demonstrate a viable route towards astronomical precision spectroscopy in the ultraviolet and may contribute to unlocking the full potential of next generation ground- and future space-based astronomical instruments.