MULTIWAVELENGTH EXCITATION BY VACUUM-ULTRAVIOLET BEAMS COUPLED WITH 4TH-HARMONICS OF A Q-SWITCHED ND-YAG LASER FOR HIGH-QUALITY ABLATION OFFUSED QUARTZ

Simultaneous irradiation of multiwavelength beams emitted from a vacuu m-ultraviolet (VUV) Raman laser offers great potential for high-qualit y microfabrication of fused quartz by ablation,In this process, short wavelength components of the beam play two roles, that is, stationary effect and transitional effect. The stationary effect means photodisso ciation of Si-O bonds and formation of metastable absorption sites to the longer wavelength beam components. The transitional effect increas es the absorption to the fundamental beam with a 266 nm wavelength fro m 0% to more than 60%. This phenomenon may be explained as the excited -state absorption (ESA) due to the coupling of the VUV laser beams wit h the fundamental beam. The mechanism of the high-quality ablation is discussed by making a comparison between these two effects. (C) 1995 A merican Institute of Physics.