Potentials and limits of mid-infrared laser spectroscopy for the detection of explosives

Optical methods are well-established for trace gas detection in many applications, such as industrial process control or environmental sensing. Consequently, they gain much interest in the discussion of sensing methods for counterterrorism, e.g., the detection of explosives. Explosives as well as their decomposition products possess strong absorption features in the mid-infrared (MIR) spectral region between lambda = 5 and 11 mu m. In this report we present two different laser spectroscopic approaches based on quantum cascade lasers (QCLs) operating at wavelengths around lambda = 5 and 8 mu m, respectively. Stand-off configuration for the remote detection of nitro-based explosives (e.g., trinitrotoluene, TNT) and a fiber coupled sensor device for the detection of triacetone triperoxide (TATP) are discussed.