Excimer laser micro machining of inorganic dielectrics

The UV-photoablation behaviour of glasses and oxide ceramics has been investigated. These materials exhibit a rather low UV-absorptivity compared to many polymers or metals. Ablation experiments were carried out with standard excimer lasers (20 ns pulse duration) and short pulse excimer lasers (500 fs). Different ablation mechanisms are found: nanosecond laser pulses lead to plasma mediated ablation in the high fluence regime, whereas the femtosecond ablation process is induced by two photon absorption. High quality imaging optics were applied to structure fused silica, borosilicate glass, and alumina with μm-resolution by ArF-laser ablation. Micromachining applications are demonstrated: (1) Ablation of dielectric multi-layer systems by laser irradiation through the transparent substrate leads to clear structures with micrometer dimensions. (2) Ablation using variable masks is utilized for the generation of three dimensional surfaces (cylindrical micro lenses).