Frequency-comb infrared spectrometer for rapid, remote chemical sensing

We demonstrate real-time recording of chemical vapor fluctuations from 22 m 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 mu m spectrum in the molecular fingerprint region is dispersed by fast heterodyne self-scanning, enabling spectra at 2 cm(-1) resolution to be recorded in 70 mu s 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. (c) 2005 Optical Society of America.