Heterodyne Spectroscopy in the THz Region with a Laser Local Oscillator

A sensitive heterodyne receiver has “been constructed for use in the submillimeter wave region. The application of a laser as a local oscillator (LO) in the fundamental mixing mode greatly improves the sensitivity compared to systems with klystron LO's in the harmonic mixing mode, especially in the 1 THz region. The possibilities for application in submillimeter spectroscopy are demonstrated with a tunable receiver for the region around 891 GHz employing an HCN laser as a LO. The high sensitivity obtained with this system shows good prospects for spectroscopy in the 1-5 THz region.