Femtosecond Laser 3D Dynamic Focusing Technology–Mirror Sandblasting and Polishing Combined Process of Monocrystalline Silicon Microlens Array Research

Monocrystalline silicon is an ideal material for infrared optics microlens arrays, achieving excellent performance, but the processing is extremely difficult and poses a challenge to traditional processing processes. In this paper, a new process flow for processing monocrystalline silicon microlens arrays is proposed, combining femtosecond laser three-dimensional dynamic focusing processing technology with sandblasting and polishing finishing technology. Dynamic focusing technology is used to adjust the focus position in real time to adapt to the complex processing needs of three-dimensional structures, and the influence of different laser processing parameters on the processing size and morphology is studied. The mechanism of processing errors and surface defects is proposed to realize the compensation of three-dimensional processing errors. Through experiments and simulations, a 515 nm green light, 100 KHz repetition frequency, power of about 20 W—maintaining the same scanning speed of 3000 mm/s and isotropic filling scanning interval of 5 μm, with an on delay of 0.23 ms, an off delay of 0.12 ms, a corner delay of 0.13 ms, and a null walk delay of 0.24 ms, and a delamination height of 1 μm—were finally selected for the laser processing. The process parameters are feasible and the processing effect is good, providing a new solution for processing hard and brittle materials.