Proposals for fabrication of long-period grating in LiNbO₃ strip waveguides

The structure of a strip LiNbO₃ waveguide clad with a planar LiNbO₃ waveguide is proposed to fabricate a long-period waveguide grating (LPWG). It is shown theoretically that an LPWG device based on such a special LiNbO₃ waveguide structure is of the merit of thermal stability The methods for fabrication of planar waveguide, channel waveguide and grating are suggested and discussed. Detailed design consideration is exemplified based on a soft-proton-exchange planar waveguide clad Ti-diffused LiNbO₃ (Z-cut) strip waveguide.