Modeling of Thermomechanical Action of Femtosecond Laser Pulses on Metallic Nanogratings

Abstract

Physical and mathematical model has been developed that makes it possible to describe a process of excitation of acoustic pulses when the energy of ultrashort laser pulses is absorbed by two-dimensional metallic nanostructures (nanogratings) deposited on a substrate of a semiconductor material. Simulation is based on the numerical solution of two-dimensional equations of motion of continuous media in the form of Lagrange, which allows calculating fields of temperature, pressure, density and velocity of particles in the medium. It is shown that deformations of metallic nanolayers, arising from their heating and further expansioncompression, are transferred into the substrate in the form of a train of acoustic pulses, the typical repetition frequency of which is in subterahertz range and is determined by the linear dimensions of nanostructures and the speed of sound in the metal.