Tunable dual-comb spectrometer for mid-infrared trace gas analysis from 3 to 4.7 {\mu}m

TL;DR

This paper introduces a tunable dual-comb spectrometer operating in the mid-infrared range (3-4.7 μm) for sensitive, high-resolution trace gas analysis, demonstrating precise measurements of various gases with high signal-to-noise ratios.

Contribution

The work presents a novel dual-comb spectrometer system based on electro-optical combs and difference frequency generation, achieving broad bandwidth and high coherence in the mid-infrared for gas sensing.

Findings

Achieved up to 454 GHz bandwidth in the mid-infrared.

Demonstrated detection of gases with ppm-level concentrations.

Maintained coherence over 3 seconds measurement time.

Abstract

Dual-frequency comb spectroscopy has emerged as a disruptive technique for measuring wide-spanning spectra with high resolution, yielding a particularly powerful technique for sensitive multi-component gas analysis. We present a spectrometer system based on dual electro-optical combs with subsequent conversion to the mid-infrared via tunable difference frequency generation, operating in the range from 3 to 4.7 $\mu$m. The simultaneously recorded bandwidth is up to 454(1) GHz and a signal-to-noise ratio of 7.3(2) x 10$^2$ Hz$^{-1/2}$ can be reached. The conversion preserves the coherence of the dual-comb within 3 s measurement time. Concentration measurements of 5 ppm methane at 3.3 $\mu$m, 100 ppm nitrous oxide at 3.9 $\mu$m and a mixture of 15 ppm carbon monoxide and 5 % carbon dioxide at 4.5 $\mu$m are presented with a relative precision of 1.4 % in average after 2 s measurement time. The noise-equivalent absorbance is determined to be less than 4.6(2) x 10$^{-3}$ Hz$^{-1/2}$.