THz generation by self-focusing of hollow Gaussian laser beam in magnetised plasma

scheme of terahertz (THz) generation is proposed by the self-focusing of a high-power laser beam having hollow Gaussian intensity profile in a collissionless magnetized plasma, where ponderomotive nonlinearity is operative. THz waves are resonantly excited at the difference frequency of laser and electron plasma wave (EPW) satisfying the proper phase matching conditions. In this paper first we have investigated the filamentation of the circularly polarized hollow Gaussian beam (HGB) propagating parallel to the direction of a static background magnetic field within the paraxial approximation, subsequently this filamented HG laser beam interplay with the electron plasma wave to generate a nonlinear current in the transverse direction, thereby producing THz radiations. The intensity of the emitted radiations are found to be highly sensitive to the order of the HGB. For the current scheme the power level of THz wave comes out to be \~ 0.05 gigawatts.