Development of a THz heterodyne receiver with quantum cascade laser and hot electron bolometer mixer for standoff detection of explosive material

The terahertz (THz) portion of the electromagnetic spectrum provides specific spectroscopic information for substance identification. It has been shown that the spectral features of explosive materials might be used for detection and identification at stand-off distances. We report on the development of a THz spectrometer for explosive detection and identification. The system is based on THz quantum cascade lasers working at different frequencies. These are used for illumination of the object under test. The reflected and backscattered radiation from the object under test is detected with a sensitive heterodyne receiver. As a first step a single frequency, liquid-cryogen free heterodyne receiver operating at 2.5 THz has been developed. In order to realize maximum sensitivity a phonon-cooled NbN hot electron bolometric mixer with a quantum cascade laser as local oscillator were chosen. The concept of the system and first results will be presented.