I disagree with the statement that LiNbO3 is difficult to etch.There are several chemical etches that work on it, plasma etching of it has been done for about 20 years, and ion beam etching will etch virtually anything. Sub-micron structures have been available for about 20 years or so. I used to run an electro-optical foundry and we routinely etched LiNbO3. Fact check before publishing please.