Comb-mode-resolved adaptive sampling terahertz dual-comb spectroscopy with a free-running single-cavity fiber laser

TL;DR

This paper presents a novel, low-complexity dual-comb spectroscopy technique in the terahertz range using a free-running single-cavity fiber laser, achieving high resolution and spectral coverage without stabilized lasers.

Contribution

It introduces a mode-resolved dual-comb spectroscopy method based on a free-running fiber laser with adaptive sampling, enabling high-resolution THz spectroscopy with simplified setup.

Findings

Achieved spectral resolution below 5 MHz

Demonstrated low-pressure acetonitrile spectroscopy

Signal-to-noise ratio of approximately 50 dB

Abstract

Mode-resolved dual-comb spectroscopy (DCS) is an emerging spectroscopic tool with the potential to simultaneously achieve a broad spectral coverage and ultrahigh spectral resolution in terahertz (THz) spectroscopy. However, the need for two independently stabilized ultrafast lasers significantly hampers the potential application of DCS techniques. In this article, we demonstrate mode-resolved DCS in the THz region based on a free-running single-cavity dual-comb fiber laser with adaptive sampling. Low-pressure spectroscopy of acetonitrile gas with absorption features approaching the Doppler limit is demonstrated by comb-mode-resolved measurements with a spectral sampling spacing of 48.8 MHz, a spectral resolution of less than 5 MHz and a signal-to-noise ratio of ~50 dB. The successful demonstration of the proposed method clearly indicates the great potential for the realization of low-complexity, MHz-resolution THz spectroscopy instrumentation.