VUV-UV multiwavelength excitation process for high-quality ablation of fused silica

Abstract

Vacuum ultraviolet (VUV) –ultraviolet (UV) multiwavelength excitation process for high-quality ablation of fused silica, in which VUV laser beam with low laser fluence and UV laser beam with relatively high fluence are simultaneously irradiated, is reviewed. Ablation mechanism is explained as absorption of the UV laser by excited-states formed by the VUV laser irradiation (excited-state absorption: ESA). A coaxial irradiation system of F 2 (157 nm) and KrF excimer (248 nm) lasers has been developed for this process. This system performs well-defined micropatterning of not only fused silica but also other advanced materials including sapphire and GaN with little thermal influence and little damage. The discussion includes characterization of optimum experimental conditions and the detailed mechanism of multiwavelength excitation process.