Frequency-comb infrared spectrometer for rapid, remote chemical sensing

TLDR

The spectrometer enables video‑rate chemical imaging and transient spectroscopy of gas plumes, flames, plasmas, and other non‑repetitive phenomena such as protein folding dynamics and pulsed magnetic fields. The study demonstrates real‑time recording of chemical vapor fluctuations from 22 m distance using a fast Fourier‑transform infrared spectrometer powered by two 10‑fs Ti:sapphire lasers. The FTIR employs a 9–12 µm broadband probe dispersed by fast heterodyne self‑scanning, producing 2 cm⁻¹ resolution spectra in 70 µs snapshots and achieving 950 spectra per second by actively adjusting one laser’s repetition rate.

Abstract

We demonstrate real-time recording of chemical vapor fluc-tuations from 22m away with a fast Fourier-transform infrared (FTIR) spectrometer that uses a laser-like infrared probing beam generated from two 10-fs Ti:sapphire lasers. The FTIR's broad 9-12 microm spectrum in the "molecular fingerprint" region is dispersed by fast heterodyne self-scanning, enabling spectra at 2cm-1 resolution to be recorded in 70 micros snapshots. We achieve continuous acquisition at a rate of 950 IR spectra per second by actively manipulating the repetition rate of one laser. Potential applications include video-rate chemical imaging and transient spectroscopy of e.g. gas plumes, flames and plasmas, and generally non-repetitive phenomena such as those found in protein folding dynamics and pulsed magnetic fields research.