Multiwavelength excitation by vacuum-ultraviolet beams coupled with fourth harmonics of a Q-switched Nd:YAG laser for high-quality ablation of fused quartz

Abstract

Simultaneous irradiation of multiwavelength beams emitted from a vacuum-ultraviolet (VUV) Raman laser offers great potential for high-quality 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 photodissociation of Si–O bonds and formation of metastable absorption sites to the longer wavelength beam components. The transitional effect increases the absorption to the fundamental beam with a 266 nm wavelength from 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 with the fundamental beam. The mechanism of the high-quality ablation is discussed by making a comparison between these two effects.