MULTIWAVELENGTH IRRADIATION EFFECT IN FUSED QUARTZ ABLATION USING VACUUM-ULTRAVIOLET RAMAN LASER

Simultaneous multiwavelength irradiation of a vacuum-ultraviolet (VUV) Raman laser presents high-quality microfabrication of fused quartz by ablation. In order to make the mechanism of high-quality ablation cle ar, both of stationary and transitional absorption changes of a fundam ental beam (266 nm) in fused quartz induced by short wavelength compon ents were examined. The stationary change is caused by photodissociati on of Si-O bonds and formation of metastable absorption sites, while t he transitional change is attributed to excited-state absorption (ESA) due to coupling of the VUV components and the fundamental beams. Comp arison of magnitude of the absorption changes between both effects ind icates that the transitional effect is dominant in the process.