Biaxial characteristics of planar proton exchanged lithium niobate waveguides

Results of a theoretical and experimental study on proton exchanged lithium niobate (LiNbO/sub 3/) planar waveguides are presented. Experimental results are successfully explained by the theoretical model only if the guiding layer is assumed to be anisotropic with biaxial characteristics, this biaxiality being induced by the proton exchange process in the uniaxial lithium niobate substrate.