Investigation of radiation mechanism in THz generation based on laser-induced plasma in air

Terahertz radiation mechanism from laser-induced plasma in air is studied through photo-current model. The effect of intensity and pulse duration of the femtosecond laser field on the spatio-temporal behavior of the photo-current is presented. The radiation pattern of such laser-induced plasma in air is calculated at THz range. It is shown that from radiation viewpoint the plasma is similar to a dipole source for low frequencies whereas for high frequencies, the plasma behaves similar to a traveling-wave current source.