Optical waveguide modes in single-crystalline LiNbO3–LiTaO3 solid-solution films

Abstract
We report new LiNbO3–LiTaO3 solid‐solution films which form excellent active optical waveguides. Measurement of the waveguide modes indicates that these films have a graded composition. To analyze these waveguides, we present a theory for the calculation of the mode indices and find that the refractive index varies with the depth in the film, according to a Fermi function.