Enhanced laser-target energy coupling through counter-propagating lasers: Insights from electron recirculation

Abstract

In the interaction between lasers of relativistic intensity and targets, a portion of the laser energy is carried by relativistic fast electrons, which usually cannot be deposited inside but escapes from the target. Here, we explored a method to reduce this energy waste and enhance laser-target energy coupling through counter-propagating lasers. Particle-in-cell simulation results show that high-energy fast electrons generated by the laser on one side can be re-accelerated by the laser on the other side through the synergistic effect of the reflected laser and longitudinal electric field after passing through the target, and then reflected back into the target by a potential barrier, forming an electron recirculation. Through this electron recirculation, the energy conversion efficiency of each laser is significantly improved, and the temperature of electrons and ions inside the target is effectively increased by 118 % and 29 %, respectively. We also explored the effects of laser intensity and target density through multiple sets of simulations with controlled variables, and summarized the electron recirculation model in such counter-propagating lasers configuration.