Generation of second harmonics by a self-focused Hermite-Gaussian laser beam in collisionless plasma

Abstract

In this work, the generation of second harmonics of a Hermite–Gaussian laser beam in collisionless plasma has been presented. On incidence of the Hermite–Gaussian laser beam in plasma, the charge carriers shift from the high field region to the low field region on account of the ponderomotive force which results in the generation of a transverse density gradient in the background plasma which in turn generates plasma waves at incident beam frequency ω0. Interaction of this plasma wave with the pump beam generates the second harmonics of the incident laser beam with frequency 2ω0. The moment theory approach has been used to derive the coupled differential equations for the beam widths of the laser beam in the transverse x- and y-directions which are further solved numerically. The effect of different modes and initial beam widths of the Hermite–Gaussian beam in the x- and y-directions has been investigated for the self-focusing and second harmonic yield (SHY) of the laser beam in plasma. Also, the effect of increasing plasma density is visualized on the self-focusing and SHY of the beam. It has been observed that the SHY significantly depends on different modes and initial widths of the Hermite–Gaussian laser beam as well as on plasma density.

Generation of one-dimensional high-order Hermite-Gaussian laser beams with large mode volume

“…Wang Xiao -Jun 1)4) Liu Bing -Jie 4) Wang Hao -Zhu 4) Yang Jun -Bo 3) Peng Qin -Jun Hermite-Gaussian (HG) beams have many important applications in the optical frontier, and the limited output power of the high-purity HG beams is partly due to the small gain volume of the mode. The commonly used off-axis end-pumped scheme offers a narrow gain volume whose diameter is about a hundred microns.…”

Second harmonic generation of high power Cosh-Gaussian beam in cold collisionless plasma

“…In this method, EPW generated at input wave frequency interacts nonlinearly with input wave resulting in the production of SHG. Major work on this mechanism has been done by various theoretical and experimental research groups in the past [40][41][42][43][44][45][46][47][48][49][50][51]. The commanding role is played by plasma wave production in laser-induced fusion due to the generation of high velocity electrons.…”