Sub-spot size CO_2 laser micromachining of features in fused silica by V-groove etching

摘要

Ablation of fused silica using the Gaussian irradiance profile of the TEM_(00) mode of a CO_2 laser is a very efficient way for micromachining features up to ten times smaller than the beam diameter. A series of laser-etched V-grooves sequentially shifted in a given fashion can be used to micromachine simple or structured patterns on the surface of fused silica substrates. Surface gratings with a periodicity of 12 μm were produced using a CO_2 laser beam of 100 μm (1/e~2) in diameter. Rectangular wells 50 μm wide and 50 μm deep were also micromachined using the same technique with a radius of curvature of roughly 8 μm at the bottom edges. Although the resolution of the periodic pattern is not fully understood, it appears to be partly governed by the amount of material removal by the top portion of the Gaussian beam (tip processing), as well as a carefully controlled shifting of the etched V-grooves on the fused silica substrate. Physical mechanisms that could be at the origin of the V shape of the grooves are also discussed.