Wet etching techniques for the realisation of novel electrode structures on X and Z-cut lithium niobate

Lithium niobate (LiNbO₃) is a popular material for the implementation of many photonic devices, but most often for broadband electro-optic (EO) modulators. Effective modulators may be realised through careful design of the RF electrodes. The most successful electrode designs incorporate some form of surface machining and thus in order to explore novel practical electrode structures, it has been necessary to develop means of etching the LiNbO₃ surface precisely. In this paper, we present the etching of LiNbO₃ using a proton exchange (PE) wet etching method including a detailed comparison of the etch properties of X and Z-cut LiNbO₃.