Multiwavelength excitation processing using F2 and KrF excimer lasers for precision microfabrication of hard materials

Vacuum ultraviolet (VUV)-ultraviolet (UV) multiwavelength excitation processing for precision microfabrication of hard materials, in which simultaneous irradiation of the VUV and the UV laser beams leads to high-quality ablation and high-efficiency modification, is reviewed. A coaxial irradiation system of F2 and KrF excimer lasers has been developed. This system achieves well-defined micropatterning of fused silica and GaN with little thermal influence and little debris deposition. Ablation mechanism is explained as absorption of KrF excimer laser by excited-states formed by F2 laser (excited-state absorption: ESA). Additionally, this technique is applied for more efficient refractive index modification of fused silica compared with single-F2 laser irradiation, which is attributed to resonance photoionization-like process based on ESA. The discussion includes characterization of optimum experimental conditions and features of the multiwavelength excitation processing