Influence of birefringence coupling on propagation constant of Ti: LiNbO3 rectangle waveguide

A new coupled-mode theory based on scalar modes is presented for the anisotropic waveguide with random disturbance via Helmholtz equation and a modified dielectric tensor. The polarization coupling term and birefringence coupling term are included in the coupling coefficient expression. In addition, the numerical modeling of the propagation is made constant for the Ti: LiNbO3 with the Marcatili's approximation and the first-order perturbation. It is found that the change of the propagation constant due to birefringence coupling is about as three percent as that due to the main perturbation term, which shows that the birefringence can not be neglected for the Ti: LiNbO3 rectangle waveguide. The work has a guidance to the study of the optical waveguide devices with the Ti: LiNbO3 waveguide.