Laser fabrication of micro sized diffractive and refractive optical devices in fused silica and glass

Laser ablation has proved to be a flexible method for direct micro-structuring of micro-mechanical, micro-fluid or micro-optical components. In this work we will present recent results on micro-machining of fused silica and different glasses. An excimer laser running at λ=248 nm (KrF) or λ=351 nm (XeF) (τ_p=20 ns) was used for the experiments. Various solutions of acetone, toluene and tetrachloroethylene containing pyrene in different concentrations (0.1-0.5 M [mol/1]) have been applied for studying the etching process. The influence of the laser and process parameters (e.g. laser fluency, scan velocity, etc.) on the etch rate and the surface roughness of the materials are investigated quantitatively with the aim of process optimization. Using these parameters the fabrication of three-dimensional micro-topographies in fused silica, pyrex and other glass by direct laser writing with the scanning contour mask technique will be shown. The etched cylindrical structures and micro-prisms show sharp edges and smooth surfaces with micro-roughness below 10 nm RMS at a etch depth of more than 30 μm. Also the machining of linear or crossed phase gratings with a period less than 20 μm is mentioned.