Mid-Infrared Standoff Spectroscopy Using a Supercontinuum Laser with Compact Fabry-Pérot Filter Spectrometers.

Mid-infrared (MIR) supercontinuum (SC) lasers are an attractive new option in the field of IR spectroscopy, especially for standoff detection. Supercontinuum radiation unites high brightness, high spatial coherence, and broadband spectral coverage, thereby surpassing thermal IR sources and challenging quantum cascade lasers. The employed SC source operates in the spectral region of 1.2-4.6 µm, filling the spectral gap where quantum cascade lasers lack broader availability. In this work, the SC radiation was recorded by compact Fabry-Pérot filter spectrometers ideally suited for sensitive standoff detection with real-time capability. The noise performance of the setup and measurements of different substances at standoff distances are presented, e.g., of different paints on a metal surface and an explosive precursor. Furthermore, the real-time capability of the setup is demonstrated by monitoring the evaporation of liquid 2-propanol.