A Microphotonic Astrocomb

TL;DR

This paper demonstrates an on-chip microphotonic astrocomb with resolvable lines, enabling precise wavelength calibration for astronomical spectrometers, which advances exoplanet detection and cosmological measurements.

Contribution

It introduces a microresonator-based astrocomb with 23.7 GHz line spacing, suitable for high-precision astronomical spectrometer calibration.

Findings

Achieved wavelength calibration at 10 cm/s radial velocity level.

Demonstrated broadband calibration potential for next-generation instruments.

Validated microresonator astrocomb's effectiveness in astronomical applications.

Abstract

One of the essential prerequisites for detection of Earth-like extra-solar planets or direct measurements of the cosmological expansion is the accurate and precise wavelength calibration of astronomical spectrometers. It has already been realized that the large number of exactly known optical frequencies provided by laser frequency combs ('astrocombs') can significantly surpass conventionally used hollow-cathode lamps as calibration light sources. A remaining challenge, however, is generation of frequency combs with lines resolvable by astronomical spectrometers. Here we demonstrate an astrocomb generated via soliton formation in an on-chip microphotonic resonator ('microresonator') with a resolvable line spacing of 23.7 GHz. This comb is providing wavelength calibration on the 10 cm/s radial velocity level on the GIANO-B high-resolution near-infrared spectrometer. As such, microresonator frequency combs have the potential of providing broadband wavelength calibration for the next-generation of astronomical instruments in planet-hunting and cosmological research.