Optical guiding of intense Hermite–Gaussian laser beam in preformed plasma channel and second harmonic generation

Arvinder Singh,Jyoti Wadhwa

doi:10.1007/s11082-021-03046-z

Abstract

This work presents the scheme of optical channeling of the intense Hermite Gaussian laser beam and second-harmonic generation in plasma having the preformed plasma channel, where relativistic nonlinearity is operative. Excitation of the electron plasma wave at the incident beam frequency leads its coupling with the latter produces the second harmonics of the beam. For the formulation of differential equations for the beam waists of the Hermite Gaussian laser beam propagating through the channel, the method of moments has been used. The solutions of the coupled differential equations are found using Runge Kutta fourth-order numerical method. Perturbation theory has been applied to find the equation governing the excitation of electron plasma wave and hence the source term for the second-harmonic yield. It has been observed that the preformed plasma channel helps to optically guide the laser beam and enhances the efficiency of second-harmonic generation of various modes of the Hermite Gaussian laser beam in plasma.

Highlights

This work presents the scheme of optical channeling of the intense Hermite Gaussian laser beam and second-harmonic generation in plasma having the preformed plasma channel, where relativistic nonlinearity is operative
It has been observed that the preformed plasma channel helps to optically guide the laser beam and enhances the efficiency of second-harmonic generation of various modes of the Hermite Gaussian laser beam in plasma
Numerical simulations have been carried out for the optical guiding as well as the second-harmonic generation of the intense Hermite Gaussian laser beam in the preformed plasma channel using the method of moments

Summary

Introduction

The study of optical guiding of the laser beam in plasma leads to the applications in fusion energy, higher harmonic generation (Gibbon 1997), laser wakefield accelerators (Clayton et al 2010), and soft x-ray laser (Nakano et al 1997). High-intensity beams are readily available these days but the challenges like beam break up due to filamentation, defocusing due to ionization, and Raman scattering is always there in the way of self-focusing of the beam These challenges can be overcome by the technique of optical guiding in which the laser beam does not create its own channel but is propagated in a preformed channel (Esarey and Sprangle 1997) These preformed channels are stable and reproducible which is the necessity for any real application. The impulse of the present work resides in investigating the effect of a preformed parabolic density channel on the optical guiding of highly intense Hermite Gaussian laser beam and the generation of second harmonics in plasma by the moment theory approach suggested by Lam et al 1977.

Guiding of Hermite Gaussian laser beam in preformed plasma channel

Density perturbation term

Second harmonic yield

Discussion of Results

Conclusions

Refrences