Effect of ionization on femtosecond laser pulse interaction with silicon

Abstract

Femtosecond laser pulse interaction with silicon is studied numerically considering the ionization process induced by the intense electromagnetic field of the laser pulse. The electromagnetic field is calculated by solving Maxwell's equations using the finite-difference time-domain method, and the two-temperature model is employed for the electron-lattice energy coupling. The electron number density is computed by an ionization model based on the energy balance of laser energy; the electrical conductivity of the dense plasma is predicted accounting for the number density and temperature of electrons. This article presents some interesting results on electromagnetic field in the silicon substrate, electron and lattice temperatures, electrical conductivity, and electron number density depending on laser pulse energy and pulse width. In particular, this study explains some physical phenomena pertaining only to femtosecond laser pulses, such as existence of threshold intensity.