Transient thermoelastic responses of dielectrics subjected to ultrashort shaped pulses

Abstract

Ultrashort laser pulse shaping is one of the crucial technologies to improve the ultrashort pulsed laser machining of dielectrics. However, the thermoelastic responses have not been considered in the previous studies in this area. This study aims to accurately predict the thermoelastic responses of dielectrics subjected to ultrashort shaped laser pulses and to provide guidance for the laser processing of dielectrics. In this paper, the Guyer–Krumhansl heat conduction and nonlocal elasticity are integrated into the theory of ultrafast laser-material interactions to accurately predict the thermoelastic responses during ultrashort shaped pulses. The evolution of electron density, electron temperature, lattice temperature, and thermal stresses are obtained using finite element method. The transient responses during two-pulse laser irradiation and the influences of pulse shaping parameters (including pulse number, separation time, and energy ratio of sub-pulses) are analyzed. Results indicate that the temperature rise during the first laser pulse is much lower than that during the subsequent pulses. The maximum value of circumferential stress at different laser parameters almost keeps unchanged due to the reduced elastic modulus. The laser parameters have significant effects on the temperature and stresses.