Abstract: An optical coupler includes a substrate and first and second elongate optical waveguides on the substrate. A structure extends along the waveguides and is configured to provide variable coupling between the waveguides. The coupler can be formed in Lithium Niobate.

Abstract: An optical polarizer is described in which a propagation layer, i.e., a titanium diffused light guiding region in a lithium niobate Z-cut crystal, is covered with a dielectric buffer layer of ZnO. The dielectric buffer layer is covered by a meal layer, typically aluminum, although gold or silver can be used. The thickness of the buffer is chosen so as to increase the attenuation of TM modes of radiation in the waveguide relative to TE modes. The buffer layer thickness can fall within a broad range and is not required to fall within a very precise range to achieve a peak level of attenuation.