Dual-comb cavity ring-down spectroscopy

TL;DR

This paper introduces dual-comb cavity ring-down spectroscopy (DC-CRDS), a novel method combining frequency combs with cavity ring-down to achieve high-resolution, broadband, and sensitive spectroscopic measurements of gases like methane.

Contribution

The paper presents a new dual-comb cavity ring-down spectroscopy technique that enables multiplexed, high-resolution, broadband measurements without sacrificing sensitivity or accuracy.

Findings

Successfully measured methane spectra with high precision.

Demonstrated two approaches leveraging dynamic cavity response.

Showed potential for trace gas detection and molecular studies.

Abstract

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 sacrificing orders of magnitude of 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. These spectra are obtained from widths and positions of cavity modes. We present two approaches which leverage the dynamic cavity response to coherently or randomly driven changes in the amplitude or frequency of the probe field. Both techniques yield accurate spectra of methane - an important greenhouse gas and breath biomarker. The high sensitivity and accuracy of broadband DC-CRDS, shows promise for applications like studies of the structure and dynamics of large molecules, multispecies trace gas detection and isotopic composition.