Effects of relativistic and ponderomotive nonlinearties on the beat wave generation of electron plasma wave and particle acceleration in non-paraxial region

Abstract

In this communication, the combined effect of relativistic and ponderomotive nonlinearities on the generation of electron plasma wave by cross focusing of two intense laser beams at difference frequency (Δω ≈ ω1 − ω2 ≈ ωp) and acceleration of electrons in laser produced homogeneous plasma is analysed in the non-paraxial region. On account of these nonlinearities, two laser beams affect the dynamics of each other, and cross focusing takes place. It is observed that the focusing of laser beams becomes fast in the non-paraxial region by expanding the eikonal and other relevant quantities up to the fourth power of the radial distance (r). Modified coupled equations for the beam width of laser beams, electric field amplitude of the excited electron plasma wave and energy gain at beat wave frequency are derived, when relativistic and ponderomotive nonlinearities are operative. These coupled equations are solved analytically and numerically to study the cross focusing of two intense laser beams in plasma and its effect on the variation of the amplitude of the electron plasma wave and energy gain. It is observed from the results that both nonlinearities significantly affect the amplitude of plasma wave excitation and particle acceleration in the non-paraxial region in comparison to the paraxial region.