Broadband Dual-Comb Spectroscopy in the Spectral Fingerprint Region

TL;DR

This paper demonstrates the extension of dual-comb spectroscopy into the 6-8 micron infrared region using femtosecond OPOs, enabling high-resolution, low-noise molecular spectra in the spectral fingerprint region.

Contribution

It introduces a novel method for applying dual-comb spectroscopy in the 6-8 micron range with femtosecond OPOs, achieving high resolution and fidelity without moving parts.

Findings

High-resolution spectra of H2O and CH4 obtained

Spectra acquired with approximately 0.3 cm-1 resolution

Spectroscopy performed in the 1285-1585 cm-1 range

Abstract

Infrared spectroscopy in the spectral fingerprint region from 6-12 um accesses the largest molecular absorption cross-sections, permitting sensitive, quantitative and species-specific measurements. Here, we show how dual-comb spectroscopy--a form of high-speed Fourier-transform spectroscopy involving no moving parts and capable of very high resolutions--can be extended to the 6-8um wavelength band using femtosecond optical parametric oscillators (OPOs). By acquiring dual-comb interferograms faster than the mutual decoherence time of the OPO combs we implement line-shape-preserving averaging to obtain low-noise, high-fidelity spectra of H2O and CH4 at approximately 0.3 cm-1 resolutions from 1285-1585 cm-1.