Investigation On Micromaching Of Sapphire By Femtosecond-nanosecond Dual-beam Laser

Sapphire has good physicochemical properties which are widely used in the fields of mechatronics,aerospace,and microelectronics.However,Because of its high hardness,high brittleness,and high price,the requirements for its processing efficiency and processing quality of sapphire are continuously increasing in industrial production,and new challenges are constantly raised in its processing technology.This topic combines the high precision of femtosecond laser machining and the high efficiency of nanosecond laser processing,proposing a method of Sapphire processing by femtosecond-nanosecond dual-beam laser which combines both processing quality and processing efficiency.In this research,the related theories of plasma physics and quantum mechanics are adapted and various laser absorption mechanisms are considered to study the absorption process and optical properties of the femtosecond-nanosecond dual-beam laser for the processed material,and analyze the energy coupling process.Fokker-plank equation,dual temperature model,and Drude model were used to study the evolution of femtosecond laser induced plasma and the interaction between plasma and incident femtosecond laser.Based on this,the energy coupling process and erosion process of nanosecond femtosecond laser and sapphire material interaction were simulated by finite element simulation.The spatio-temporal evolution of plasma density and its effect on the absorption coefficient,reflectivity,etc.,and the law of erosion are studied.Based on the theoretical research,a femtosecond-nanosecond laser processing platform was built.Then,Femtosecond and femtosecond-nanosecond laser sapphire process experiments were carried out.The same process parameters as the simulation analysis were used to study the effects of laser single pulse energy and the number of pulses on the micro-hole machining to verify the simulation results.The effects of different pulse delay,laser power,laser repetition frequency,scanning speed,and number of scans on the surface morphology and depth of the scratched sapphire microgroove were studied.The research results show that the femtosecondnanosecond pulse delay can significantly affect the energy coupling and processing efficiency between the laser and the material.The reasonable selection of the laser frequency and the number of scans can further improve the microgroove processing quality.This research has important implications for the further study of the interaction between laser and sapphire and the formation of a new high-efficiency precision machining method for wide bandgap semiconductor materials.