Leaky Mode Propagation in Planar Multilayer Birefringent Waveguides: Longitudinal Dielectric Tensor Configuration

In this paper we examine leaky mode propagation in a general five-layered c-rotated optical structure with longitudinal dielectric tensor configuration that can be considered a useful pattern for many actual waveguides. The dependence of the leaky mode propagation on the longitudinal angle phi (between the optical c-axis and laboratory axis) is shown and the dispersion characteristics for different types and thicknesses of buffer and metal layer are reported. The guided mode losses at the wavelength lambda = 0.633 mum assume the lowest values (about 1 dB/cm) for an Ag layer and for phi = 0-degrees. Furthermore, we investigate the variation in the propagation characteristics of the leaky and guided modes with respect to the source wavelength. We obtain the transition wavelength from (G) guided modes to lowest order (L1) leaky mode, having the ordinary component that leaks into the substrate; the transition wavelength to a higher order (L2) leaky mode, which has both ordinary and extraordinary leaky components and the leaky cutoff wavelength. As an example, for phi = 10-degrees and an Ag metal layer, the first-order G11 mode transforms from guided to leaky L11(1) at lambda(gl) congruent-to 0.9 mum. The losses exhibit a change of several dB near the wavelength transition from guided to leaky mode (e.g. the attenuation constant of the G11 mode changes from 0.26.10(2) dB/cm at lambda = 0.633 mum to 0.18.10(5) dB/cm at lambda = 0.95 mum where its ordinary component is a leaky one). A similar change is found near the transition wavelength from a lowest-order mode to the highest-order leaky mode.