Experiment And Simulation Of Microstructure Machining On Quartz Glass By Femtosecond Laser

Quartz glass has many advantages such as high mechanical strength, high heat tolerance, small coefficient of thermal expansion, so it is widely used in many fields such as lithographic printing, space optical and laser fusion system. In these fields, it is often involved with the precision machining of microstructure, such as the surface groove manufacturing and surface flute thinning. Because of the high hardness and fragility of quartz glass, it is difficulty for traditional methods such as photolithography, ultrasound and ions etching to fabricate micro structures on the surface. The pulse width of femtosecond is shorter than the character time of most physical-chemical processes, so it has many advantages such fixed threshold, extremely narrow HAZ, small recast and high reliability, which makes the machining possible. So far the femtosecond laser ablation mechanism of quartz glass is not deeply recognized, the simulation model of groove and flute is not well built, and the key manufacturing process of flute thinning is imperfection. The shape and morphology research of microstructure machining on quartz glass by femtosecond laser was investigated with experimental and simulation methods in this paper. The specific work was presented as follows:(1) The nonlinear process in femtosecond laser ablation dielectrics was analyzed, the ablation theoretical models were built based on the Fokker-Planck equations, and the ablation threshold and rate were calculated. It provides pulse energy reference for subsequent microstructure machining and theoretical basis for the building of simulation models.(2) The micro-crater ablation experiments were carried out to analyze the influences of pulse energy and number on the morphology and shape of micro-crater. The values of ablation threshold, ablation rate and multi-pulse accumulation coefficient were measured to validate the threshold simulation result and support basic parameters for subsequent microstructure simulation models.(3) The micro-line ablation experiments were carried out to analyze the influences of pulse energy and scanning speed on the morphology and shape of micro-line, and the tuning parameters of micro-line ablation were determined. The cross-section shape simulation model of micro-line was built, and it provides the foundation for the simulation of flute thinning.(4) The single-layer micro-flute ablation experiments were carried to analyze the influences of line overlap rate on the morphology and shape of micro-flute. The 3D one-layer micro-flute simulation model was built to analyze the influences of pulse energy and scanning speed on the bottom roughness.(5) Compared with the single-layer ablation micro-flute, the double-layer micro-flute ablation experiments were carried to analyze the influences of thinning methods on the quality of micro-flute.