Cavity-enhanced dual-comb spectroscopy

TL;DR

This paper introduces a novel cavity-enhanced frequency comb Fourier transform spectroscopy method that enables ultrafast, broad-bandwidth, high-resolution molecular spectra measurement with high sensitivity, suitable for time-resolved studies.

Contribution

It presents a new approach that overcomes previous analysis challenges, allowing rapid, ultrasensitive spectral measurements across broad spectral ranges without detector arrays.

Findings

Recorded spectra of ammonia within 18 μs

Achieved a noise-equivalent-absorption of 3×10^-12 cm^-1Hz^-1/2

Demonstrated potential for time-resolved spectroscopy of fast events

Abstract

The sensitivity of molecular fingerprinting is dramatically improved when placing the absorbing sample in a high-finesse optical cavity, thanks to the large increase of the effective path-length. As demonstrated recently, when the equidistant lines from a laser frequency comb are simultaneously injected into the cavity over a large spectral range, multiple trace-gases may be identified within a few milliseconds. Analyzing efficiently the light transmitted through the cavity however still remains challenging. Here, a novel approach, cavity-enhanced frequency comb Fourier transform spectroscopy, fully overcomes this difficulty and measures ultrasensitive, broad-bandwidth, high-resolution spectra within a few tens of $\mu$s. It could be implemented from the Terahertz to the ultraviolet regions without any need for detector arrays. We recorded, within 18 $\mu$s, spectra of the 1.0 $\mu$m overtone bands of ammonia spanning 20 nm with 4.5 GHz resolution and a noise-equivalent-absorption at one-second-averaging per spectral element of 3 10^-12 cm^-1Hz^-1/2, thus opening a route to time-resolved spectroscopy of rapidly-evolving single-events.