LASER-INDUCED PLASMA-ASSISTED ABLATION OF FUSED QUARTZ USING THE 4TH HARMONIC OF A ND-YAG LASER()

A novel method of micromachining fused quartz by laser-induced plasma- assisted ablation using the fourth harmonic of a Nd+:YAG laser (266 nm ) is reported. With the assistance of plasma resulting from laser irra diation on a metal target, the fused-quartz substrate is easily etched by the 264-nm laser beam in spite of the fact that the substrate is t ransparent to this wavelength. In contrast, no ablation takes place wi thout the metal target, but damage is generated on the substrate surfa ce. The ablated region is observed by optical microscopy and scanning probe microscopy (SPM), which reveal a fine grating structure (line sp acing of 20 mu m) without any severe damage. A series of experiments o n the dependence of the ablation rate and the threshold laser fluence on ablation parameters, such as laser fluence, the number of pulses, a nd the distance between the fused quartz and the metal target is perfo rmed. On the basis of the results, three possible mechanisms of direct plasma interaction, plasma heating, and metal film deposition are dis cussed.