Fabrication of ridge waveguides in LiNbO3

We have fabricated ridge waveguides in lithium niobate with sidewall roughness of 14 nm (rms) and sidewall angles of more than 71°. The use of thick electroplated metal masks for reactive ion etching (RIE) makes it possible to manufacture ridge structures with several microns in height. For light confinement towards the substrate we investigate direct heterobonding techniques. Due to the expected low transmission losses we envision future applications in the field of quantum optics.