An As40Se50-xSxGe10 film strip loaded waveguide, formed in the graded-index LiNbO3 planar waveguide, has been demonstrated. Analytical results show that the optical field confinement in the waveguide loaded by the high refractive index film becomes large near the film cutoff thickness for the fundamental mode. Photostructural effect of the chalcogenide glass overcomes difficulty in precisely controlling film thickness. A 3-D waveguide has been achieved by loading As40 Se10S40Ge10 film 10 µm wide on a Ti diffused LiNbO3 planar waveguide. Optical confinement in the waveguide has been improved intensively with the aid of the photostructural effect of the film.
Juichi Noda, Sakae Zembutsu, Shuzo Fukunishi, and Naoya Uchida, "Strip-loaded waveguide formed in a graded-index LiNbO3 planar waveguide," Appl. Opt. 17, 1953-1958 (1978)