On-chip dual-comb source for spectroscopy

Abstract

Dual-comb spectroscopy is a powerful technique for real-Time, broadband optical sampling of molecular spectra, which requires no moving components. Recent developments with microresonator-based platforms have enabled frequency combs at the chip scale. However, the need to precisely match the resonance wavelengths of distinct high quality-factor microcavities has hindered the development of on-chip dual combs. We report the simultaneous generation of two microresonator combs on the same chip from a single laser, drastically reducing experimental complexity. We demonstrate broadband optical spectra spanning 51 THz and low-noise operation of both combs by deterministically tuning into solitonmode-locked states using integratedmicroheaters, resulting in narrow (<10 kHz) microwave beat notes. We further use one comb as a reference to probe the formation dynamics of the other comb, thus introducing a technique to investigate comb evolution without auxiliary lasers or microwave oscillators. We demonstrate high signal-To-noise ratio absorption spectroscopy spanning 170 nm using the dual-comb source over a 20-ms acquisition time. Our device paves the way for compact and robustspectrometers at nanosecond time scales enabled by large beat-note spacings (>1 GHz).