Femtosecond laser-assisted etching is a technique for internal micro removal processing of transparent materials. In the present study, we applied this technique to fluoride crystals of CaF 2 and MgF 2. In the case of CaF 2, selective etching of a femtosecond laser-modified region was observed with etchants of aqueous solutions of nitric acid, sulfuric acid, and hydrogen chloride, while no signature of etching was observed for MgF 2. Microchannels were fabricated in CaF 2 substrates. At the inlet, the microchannel showed polygonal shapes, which may be related to anisotropy in the etching rate.
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