激光诱导等离子体加工石英微通道机理研究

利用调Q的Nd: YAG激光器输出的纳秒激光脉冲诱导等离子体加工石英微通道, 显微镜下观察微通道深度可达4 mm, 通道周围没有发现热裂纹, 围绕通道内壁产生了固化层. 研究了纳秒脉冲下固体材料损伤的电离机理. 波长为1064 nm, 光强不很强的纳秒脉冲作用时, 光学击穿中等离子体的形成主要是雪崩电离的结果, 利用雪崩击穿的阈值理论得到了等离子体形成模型, 求出了等离子体形成范围, 理论模型结果与实验结果基本相符.最后基于激光支持的爆轰波模型, 利用流体力学理论求出了等离子体的温度、 速度、 压强等特征参数, 并分析了微通道的特点.高温高压的等离子体烧蚀出石英微通道, 等离子通过后, 在冲击波压力作用下微通道内壁熔化的 石英凝固形成固化层.

Study on the machining mechanism of fabrication of micro channels in fused silica substrates by laser-induced plasma

A Q-switched Nd: YAG laser was used to fabricate micro channels in the fused silica substrate by laser-induced plasma. The micro channels were observed with fluorescence microscope, no thermal cracks around the channels and the depth of the channels is up to 4 mm. There are coagulation layers around the inner surface. We studied the ionization mechanism of optical breakdown in solids by nanosecond laser pulses. For the 1064 nm laser, as the intensity of nanosecond pulse is not enough large, plasma formation in optical breakdown is the result of an electron avalanche process. We got the plasma formation model using the breakdown threshold of avalanche ionization and calculated the range of laser plasma based on the model. The theoretical analysis based on the model is shown to be mainly agreement with the experimental observations. The laser-supported detonation wave (LSDW) based on the principle of hydrodynamics was analyzed as well and calculated the characteristic parameters of plasma including the plasma temperature, pressure and velocity. The characteristics of micro channels were analyzed through the parameters. When the plasma passed, the melting quartz solidified with the effect of LSDW and produced the coagulation layers. The ablation of the high temperature and pressure plasma lead to a micro channel of high quality with a relatively smooth internal surface and no thermal cracks.