Terahertz continuous wave nonlinear-optical detection without phase-locking between a source and the detector

We demonstrate the possibility of nonlinear-optical detection of terahertz (THz) wave radiation without phase-locking between a source and a detector. Spectrally resolved room-temperature incoherent nonlinear-optical detection is demonstrated for 0.22-THz continuous wave (CW) radiation by upconversion using a 100-mW CW laser in a 15-mm-long Mg:LiNbO3 crystal.