Femtosecond-Laser Assisted Selective Etching of Microchannels in Lithium Niobate

Selective etching of femtosecond (fs) laser-modified material is a unique technique for creating 3d hollow microstructures inside transparent dielectrics. An ultrashort pulse laser beam is tightly focused into the sample so that a material modification limited to the focal volume is
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induced via nonlinear absorption. By translating the sample relative to the laser beam, structures of modified material can be inscribed. The laser-modified material has a higher etching rate than unmodified material in a suitable etching solution, enabling etching of ultrahigh aspect ratio (~1000) microchannels inside the sample volume. This method is well established in glass and also known for few crystals [1]. So far, this is the only method to create holes of said dimensions inside the sample volume without any need for sandwich structures.