Vilnius university , Lithuania

Terahertz (THz) radiation generation during the laser-air interaction is investigated both experimentally and theoretically. For the experiments a regeneratively amplifed 1 kHz repetition rate femtosecond Ti:Sapphire laser system delivering single pulses (with pulse duration of about 100 fs) of 3 mJ maximal energy at 804 nm central wavelength has been used. The linearly polarized laser pulses were focused into the ambient air by the lens of about 15 cm focal length through the thin nonlinear BBO crystal. The emitted THz radiation was collimated by an off-axis parabolic mirror and then focused with the second one onto a 0.5 mm thick ZnTe crystal for the electrooptic characterization. The dependencies of THz yield on the pump power, polarization angle of the fundamental wave and the position of the nonlinear crystal were registered and a good agreement with the theoretically predicted data has been obtained.