A VECSEL-based virtually imaged phased array spectrometer for rapid gas phase detection in the mid-infrared

We present a novel system for high-resolution, time-resolved spectroscopy in the mid-wave infrared based on a modelocked vertical external cavity surface emitting laser (VECSEL) frequency comb coupled to a virtually imaged phased array (VIPA) spectrometer. The GHz level repetition rate of VECSEL based systems coupled to VIPA spectrometers enables comb-tooth resolved spectra without the use of additional filter cavities often required to increase comb tooth spacing. We demonstrate absorption spectroscopy on a methane (CH₄) gas mixture at 2900 cm-1 (3.4 μm) with over 35 cm−1 spectral bandwidth in a single image. Rapid time-resolved measurements were made using a 300 μs exposure time with an acquisition rate limited to 125 Hz by the available camera. High-resolution absolute frequency measurements were performed by scanning the repetition rate of the VECSEL frequency comb.