Spectroscopic detection of hazardous substances using broadband-tunable quantum cascade lasers

Broadband tunable external cavity quantum cascade lasers (EC-QCL) [1] are very attractive light sources for mid-infrared (MIR) spectroscopy. Here we report on EC-QCL based spectroscopic detection of hazardous substances, focusing on two application examples: Stand-off detection of explosives and sensing of dangerous contaminations in water. Our standoff-system provides contactless identification of solid residues of different explosives over distances of several meters. In our setup for MIR absorption spectroscopy on liquids, the EC-QCL enables the use of a transmission cell with an extended optical path length of 100 m despite the strong background absorption of water.