Terahertz photomixing spectrometer technology

Photomixers are used to generate THz radiation by mixing two near infrared lasers. The frequency of the radiation is sweepable from 100 GHz to 3 THz which makes them very useful for THz spectroscopy. An important performance indicator of sensitive THz detectors is the spectral response. A photomixing spectrometer is used to measure the spectral responsivity of several direct detectors such as bolometers and Schottky rectifiers. This work also contains an analysis of a coherent photomixing transceiver, in which a signal is upconverted to Terahertz frequencies by a transmitting photomixer and downconverted with a receiving photomixer. The transceiver is used to measure the amplitude and phase response of transmission through materials. Developed techniques are used to measure transmission spectra of clothing, BZN, biotin, water,and carbohydrates. In particular, lactose reveals interesting solid state physics phenomena at THz frequencies.