Investigation on sapphire ablation by femtosecond-nanosecond dual beam laser

Abstract

Sapphire as a typical wide bandgap semiconductor material, has good physical and chemical properties and is widely used in mechanical electronics, aerospace, microelectronics and other fields. In order to improve ablation efficiency and at the same time ensure the processing quality, the ns-fs dual beam laser ablation method is proposed to process sapphire, which utilizes the high peak power of femtosecond pulses to excite free electrons through multiphoton ionization and collision ionization and the relatively larger fluence of nanosecond laser to improve the processing efficiency. In order to reveal the energy coupling mechanism between ns-fs dual beam laser and sapphire material, Fokker-Plank equation, Drude model and two-temperature model were used to study the evolution process of free electrons induced by femtosecond laser and the interaction between free electrons and incident laser. The energy coupling process and ablation process were simulated by finite element method, and the space-time evolution law of electron densities and its influence on surface optical properties such as absorption coefficient and reflectivity under different pulse delays were studied to reveal the mechanism of high-efficiency and high-quality processing of sapphire by ns-fs dual beam laser. This research is of great significance to the high-efficiency and high-quality processing of brittle and hard materials.