Guided modes of Ti:LiNbO3 channel waveguides: a novel quasi-analytical technique in comparison with the scalar finite-element method

Two different techniques for the calculation of optical modes of Ti:LiNbO₃ channel waveguides are presented. The first one is an almost analytical technique based on the effective-refractive-index method. The second one is based on the well-known finite-element method. Both approaches use a rather realistic waveguide model considering crystal anisotropy, wavelength dispersion of the refractive index distributions, and also the nonlinear dependence of the ordinary refractive index on the Ti⁴⁺ concentration. Effective indices and field distributions obtained by both techniques are compared for wavelengths of 0.6 and 1.2 μm, for both quasi-TE and -TM polarization, considering Y-cut and Z-cut crystal orientation and both isotropic and anisotropic Ti⁴⁺ diffusion