Femtosecond Laser-Assisted Etching of Fluoride Crystals

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.