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 tenser configuration that can be considered a useful pattern for many actual waveguides. The dependence of the leaky mode propagation on the longitudinal angle /spl 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 /spl lambda/=0.633 /spl mu/m assume the lowest values (about 1 dB/cm) for an Ag layer and for /spl phi/=0/spl deg/. 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 (L/sup 1/) leaky mode, having the ordinary component that leaks into the substrate; the transition wavelength to a higher order (L/sup 2/) leaky mode, which has both ordinary and extraordinary leaky components and the leaky cutoff wavelength. As an example, for /spl phi/=10/spl deg/ and an Ag metal layer, the first-order G/sub 11/ mode transforms from guided to leaky L/sub 11//sup 1/ at /spl lambda//sub gl//spl sime/0.9 /spl mu/m. The losses exhibit a change of several dB near the wavelength transition from guided to leaky mode (e.g. The attenuation constant of the G/sub 11/ mode changes from 0.26/spl times/10/sup 2/ dB/cm at /spl lambda/=0.633 /spl mu/m to 0.18/spl times/10/sup 5/ dB/cm at /spl lambda/=0.95 /spl mu/m 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.<
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