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

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.