Simulation of ultra-relativistic dynamics of electrons in the interaction of a short-intense laser pulse with plasma

Abstract

This paper presents numerical simulations of the interaction of an ultraintense laser field with a single electron and studies the nonlinear plasma effects produced when an ambient harmonic restoring force is considered during the relativistic acceleration of the particle. The motion of a charged particle in a strong laser pulse of varying wave form and polarization is explored. Mainly, the objective is to study how linear polarization leads to different energy distributions for electrons stripped from atoms by the laser field. The numerical solutions that make use of the variable-step Runge-Kutta technique are presented and describe the relativistic dynamics of a single charged particle in plasma, through the relativistic equations of motion. A harmonic restoring force is used as a simple model to simulate charge separation effects and the generation of electrostatic forces during the laser field interaction in a plasma. The motion of the relativistic electron is discussed at length considering different initial conditions for time-varying pulse intensities. The dynamics of particles at rest are studied before the interaction with the laser pulse. In addition, the time dependent longitudinal momentum for various pulse intensities is compared after the interaction with the laser for a range of optical cycles. Specifically, we focus on the time dependence of the longitudinal momentum with linear polarization for different laser intensities. In addition to the longitudinal position and momentum, the effect of the residual momentum and energy of the electrons in the plasma is carefully studied. It was found a strong dependence of the residual momentum on plasma density and laser intensity for a number of ultra-relativistic laser-plasma scenarios considered