Optical rectangular waveguide in titanium-diffused lithium niobate having its optical axis in the transverse plane

The complex equivalent propagation constants and the field distributions of the hybrid Epqx and Epqy modes of a lossy rectangular waveguide, including a metal film and a dielectric overlay, are derived using the effective-refractive-index method. The effects of the lossy metal cladding and of the direction of the birefringent medium c axis on the electromagnetic waves are examined. In particular, a two-dimensional analysis, required by the method employed, is carried out for any angle θ defining the c orientation with respect to the x direction in the plane transverse to the waveguide axis. We find at θ = 39° a turning point between the TE-like and TM-like polarizations for the well-guided ordinary wave. Investigation of a three-dimensional guide is accomplished for horizontal and vertical c-axis orientation. The modal characteristics of the lossy structure differ little from those obtained from the lossless and first-order perturbation approximate solutions. The results are given in numerical and graphical forms.