Effect of plasma formation on the double pulse laser excitation of cubic silicon carbide

TL;DR

This study uses time-dependent density functional theory to analyze how plasma formation affects the efficiency of double pulse laser excitation in cubic silicon carbide, revealing that plasma dynamics significantly influence excitation outcomes.

Contribution

It introduces three approaches to model plasma formation during double pulse laser excitation in 3C-SiC, highlighting the impact of plasma state on excitation efficiency.

Findings

Plasma formation alters the excitation efficiency.

Lower electron temperature increases excitation efficiency.

Simple double pulse approach is less accurate.

Abstract

We calculate the electron excitation in cubic silicon carbide (3C-SiC) caused by the intense femtosecond laser double pulses using time-dependent density functional theory (TDDFT). We assume the electron distributions in the valence band (VB) and the conduction band (CB) based on three different approaches to determine the dependence of the plasma that is formed on the excitation by the first pulse. First, we consider the simple double pulse irradiation, which does not include the electron-electron collisions and relaxation. Second, we consider the partially thermalized electronic state, in which the electron temperatures and numbers in the VB and the CB are defined independently. This assumption corresponds to the plasma before the electron-hole collisions becomes dominant. The third approach uses the fully thermalized electron distribution, which corresponds to a timescale of hundreds fs. Our results indicate that the simple double pulse approach is the worst of the three, and show that the plasma formation changes the efficiency of the excitation by the second pulse. When the electron temperature decreases, the laser excitation efficiency increases as a result.