Lithium niobate devices fabricated using deep ultraviolet radiation

A device, comprising:

• a lithium niobate waveguide having a lithium niobate sidewall, the lithium niobate sidewall having a short range root mean square roughness of less than ten nanometers;
• and
• wherein the lithium niobate sidewall is fabricated using photolithography, a first etch and a second etch, the photolithography using light to form a mask for fabricating a hard mask from a hard mask layer, the hard mask layer being provided on a lithium-containing layer, a stop layer being provided on the lithium-containing layer, the hard mask layer residing on the stop layer, the stop layer being sandwiched between the hard mask layer and the lithium-containing layer, the stop layer being insensitive to an etch of the hard mask, the first etch for removing a portion of the hard mask layer to form the hard mask that includes depression over a portion of the lithium niobate, a pattern from the mask being transferred to the hard mask layer to form the hard mask via the first etch, wherein the forming of the hard mask further includes forming at least one aperture in the hard mask, the at least one aperture corresponding to the pattern and exposing a portion of the stop layer residing on a region of the lithium-containing layer to be removed, the second etch removing the portion of the lithium niobate exposed by the hard mask to form the lithium niobate sidewall, such that the sidewall has the short range root mean square roughness of less than ten nanometers.

A method of providing an optical device, comprising:

• providing a waveguide including lithium niobate and having a lithium-containing sidewall, the lithium-containing sidewall having a short range root mean square roughness of less than ten nanometers, the lithium-containing sidewall being a lithium niobate containing sidewall;
• and
• wherein the lithium-containing sidewall is fabricated using photolithography, a first etch and, and a second etch that removes a portion of a lithium-containing material to form the lithium-containing sidewall, the photolithography using light to form a mask for fabricating a hard mask from a hard mask layer, the hard mask layer being provided on a lithium-containing layer, a stop layer being provided on the lithium-containing layer, the hard mask layer residing on the stop layer, the stop layer being sandwiched between the hard mask layer and the lithium-containing layer, the stop layer being insensitive to an etch of the hard mask, a pattern from the mask being transferred to the hard mask layer to form the hard mask via the first etch, wherein the forming of the hard mask further includes forming at least one aperture in the hard mask, the at least one aperture corresponding to the pattern and exposing a portion of the stop layer residing on a region of the lithium-containing layer to be removed, the second etch being different from the first etch and being selected from a dry etch, a reactive ion etch (RIE), a plasma etch and a chemical etch, such that the lithium-containing sidewall has the short range root mean square roughness of less than ten nanometers.