A finite-difference frequency-domain method for full-vectorial mode solutions of anisotropic optical waveguides with arbitrary permittivity tensor.

A new finite-difference frequency-domain (FDFD) method based eigenvalue algorithm is developed for analyzing anisotropic optical waveguides with an arbitrary permittivity tensor. Yee's mesh is employed in the FD formulation along with perfectly matched layer (PML) absorption boundary conditions. A standard eigenvalue matrix equation is successfully derived through considering simultaneously four transverse field components. The new algorithm is first applied to the mode solution of a proton-exchanged LiNbO(3) optical waveguide and the results agree with those obtained using a full-vectorial finite-element beam propagation method. Then, the algorithm is used to study modes on a liquid-crystal optical waveguide with arbitrary molecular director orientation. This arbitrary orientation may cause the loss of transverse-axis symmetries of the waveguide with symmetric background structure. Asymmetric mode-field profiles under such situations are clearly demonstrated in the numerical examples.