ИСТИНА

Abstract (About 500 words) THz radiation has a wide variety of applications in material science, medicine, biology, non-destructive testing and other areas of fundamental research, applied science and engineering. Broadband THz sources are of particular importance here. High peak power femtosecond lasers provide different ways to generate such pulses. This paper describes two approaches based on TW high repetition rate Ti:Sa laser: DC field enhanced remote production from air filament and THz unipolar pulses from relativistic laser plasma interaction. Femtosecond filamentation in air is known as a very promising source of THz pulses. Different schemes were developed to enhance efficiency, and among them the scheme with an external DC field looks especially interesting for the remote applications. Our experiments proved that maximum THz efficiency can be achieved if DC electrodes have the same length as the single-color filament and this scheme is efficient even at long distances from the laser source. The main drawback of all the approached based on non linear conversion of femtosecond laser pulses into THz range is intensity limitations (filamentation in air, lithium niobate or organic molecular crystals, etc.). This limitation can be avoided if plasma is used instead. Here we report on our progress toward generation of sub cycle (quasi unipolar) THz pulses from relativistic laser interaction of laser pulse with thin plasma slab. Various approaches and optimization of the THz sources are presented.