Long-wave infrared Fourier transform spectroscopy with enhanced and scalable sensitivity

TL;DR

This paper introduces a broadband long-wave infrared Fourier transform spectrometer that significantly surpasses previous sensitivity levels by integrating dual-comb spectroscopy, electro-optic sampling, multi-channel detection, and GPU-based corrections.

Contribution

The work presents a novel spectrometer architecture that achieves enhanced sensitivity and scalability for LWIR spectroscopy, enabling rapid multispecies gas analysis.

Findings

Detection limits of 0.3 ppb for NH3 and 2 ppb for C2H4 in 500 s

20x and 40x sensitivity improvements over previous LWIR methods

High spectral resolution of 0.0027 cm$^{-1}$ with broad coverage

Abstract

We report a broadband long-wave infrared Fourier transform spectrometer with sensitivity exceeding that of previously reported direct-detection implementations. The system combines dual-comb spectroscopy with electro-optic sampling, multi-channel parallel near-infrared detection using InGaAs photodiodes, and real-time GPU-based computational corrections of multiple spectroscopy signals. Detection limits of 0.3 ppb for NH$_{3}$ and 2 ppb for C$_{2}$H$_{4}$ are achieved in 500 s, corresponding to 20x and 40x sensitivity improvements over earlier LWIR demonstrations, while maintaining high 0.0027 cm$^{-1}$ spectral resolution and broad spectral coverage. The architecture supports scalable sensitivity through increased detector count and enables rapid multispecies analysis of complex gas mixtures.