Tunable Active HEterodyne Terahertz Imager (TAHETI)

LongWave Photonics, Massachusetts Institute of Technology and Virginia Diodes are proposing the use of the Terahertz Quantum-Cascade Lasers (QCL) combined with a Schottky diode detector for high dynamic range heterodyne imaging. Two single-mode, distributed feedback (DFB) QCLs with milliwatt power levels will be used as local oscillator and illumination for imaging. The QCLs will be downconverted 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 rates. Arrays of DFBs designed for different frequencies will allow tunability over the 2 to 5 THz frequency range. This system will enable non-destructive, non-contact testing of materials that are transparent in the terahertz band, potentially revealing information that is complementary to other imaging modalities.