3D-microstructuring of sapphire using fs-laser irradiation and selective etching

We demonstrate a technique called ""In volume Selective Laser Etching"" (ISLE) for fs laser mi-cro structuring of sapphire with subsequent wet etching in HF acid for the formation of microchan-nels and hollow volumes. In the process the sapphire sample is irradiated and by that modified with tightly focused fs-laser radiation as well on the surface as in the volume. Afterwards the sample is etched for about 48 hours in a 48% hydrofluoric acid to remove the modified material. Due to the non-linear absorption process in transparent materials a complete variability in three dimensions is given. This allows the modification also in the volume of sapphire samples for the fabrication of, e.g micro channels and hollow volumes,, which are needed for micro fluidic applications. More over ISLE can be used as a kind of cutting process to fabricate 3D micromechanical devices with high precision and without after treatment like polishing. The average surface roughness which can be reached with this method is 64 nm.