High-speed single-pixel long-wave-infrared trace chemical detection system

A standoff chemical detection system was developed to rapidly detect trace chemicals on surfaces. In only 0.1 s, the system can measure the long-wave infrared (LWIR) spectral reflectance from a surface over the wavelength range of 7.5 – 10.5 μm with a spectral resolution of 2 cm^-1. Under these conditions, a signal-to-noise ratio (SNR) > 100 was demonstrated at standoff distances of 0.5 – 1.5 m. As a detection example, saccharin was detected on high-density polyethylene (HDPE) at a surface concentration of 30 μg/cm². The high-speed acquisition capability was made possible by combining a thermoelectrically cooled single-pixel HgCdTe (MCT) detector, advanced acquisition electronics, and fast-tuning external-cavity quantum cascade lasers (EC-QCLs).