High Dynamic Range Heterodyne Terahertz Imager

The Tunable Active HEterodyne Terahertz Imager (TAHETI) system will use Terahertz Quantum-Cascade Lasers (QCL) combined with a Schottky diode detector for ultra-high dynamic range heterodyne imaging. Distributed feedback (DFB) QCLs with milliwatt power levels are engineered to emit at slightly offset frequencies, and are used as local oscillator and illumination for imaging. The QCLs will be down converted to an IF band in a reference and a signal Schottky diode mixer. High-dynamic ranges of>90 dB are estimated for real-time image acquisition. Arrays of DFBs designed for different frequencies will allow tunability in the THz frequency range. This system will enable nondestructive, non-contact testing of materials that are transparent in the terahertz band, potentially revealing information that is complementary to other imaging modalities