LAUSR

This paper presents a scheme to achieve THz radiation by the beating of two laser beams in a plasma. Lasers are obliquely incident on an underdense plasma with density ripples. Lasers having different frequencies and wave numbers but the same electric fields exert a ponderomotive force on the plasma electrons at the beating frequency which creates THz waves. The general formulas for the efficiency and THz field amplitude with arbitrary laser beam profiles (such as super-Gaussian and triangular) are derived where the effect of electron-neutral collisions is taken into account. The results show that the efficiency of THz radiation is sensitive to the angle of incidence, beam profile, collision frequency, and beating frequency. The most striking feature of this paper is that with obliquely incident laser beams, higher efficiency can be reached for collisionless and collisional plasma compared to normal incidence.