Similarity of angular distribution for THz radiation emitted by laser filament plasma channels of different lengths.

The influence of plasma channel length on an angular terahertz (THz) radiation distribution is experimentally studied for the channel formed under filamentation of an ultrashort laser pulse. It is shown that the angular distribution of the THz emission depends only on laser intensity in the filament and plasma density of the plasma channel and does not depend on the plasma channel length. A qualitative explanation of the THz emission screening by the filament plasma channel is proposed.

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.