Long path length cw-THz spectrometer using a multipass cell

摘要

Multipass cells have been extensively used in the infrared. Their use at THz frequencies is minimal due to the difficulty of coupling the highly divergent THz beams. The divergence of a cw-THz photomixing source was characterized and included in a beam propagation calculation to match the THz beam to a multipass cell. Path lengths up to 20m have been realized. The spectra of carbonyl sulfide (OCS), vinyl chloride (CH2CHCl) and dimethyl sulfoxide (DMSO), (CH3)2SO are used to demonstrate the improved sensitivity of the spectrometer.