On-chip dual comb source for spectroscopy

TL;DR

This paper presents the first on-chip dual microresonator comb source generated from a single laser, enabling broadband, high-SNR spectroscopy and dynamic comb evolution studies without external lasers.

Contribution

It introduces a novel on-chip dual comb source from a single laser, overcoming resonance matching challenges and enabling real-time spectroscopy and comb dynamics investigation.

Findings

Broadband combs spanning 51 THz around 1.56 μm

Narrow microwave beatnotes (<10 kHz) indicating low noise

High-SNR absorption spectroscopy over 170 nm in 20 μs

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 an on-chip dual comb source. Here, we report the first simultaneous generation of two microresonator combs on the same chip from a single laser. The combs span a broad bandwidth of 51 THz around a wavelength of 1.56 $\mu$m. We demonstrate low-noise operation of both frequency combs by deterministically tuning into soliton mode-locked states using integrated microheaters, resulting in narrow ($<$ 10 kHz) microwave beatnotes. We further use one mode-locked 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 broadband high-SNR absorption spectroscopy of dichloromethane spanning 170 nm using the dual comb source over a 20 $\mu$s acquisition time. Our device paves the way for compact and robust dual-comb spectrometers at nanosecond timescales.