Light scattering from periodic refractive-index fluctuations in asymmetric slab waveguides

We consider scattering of light out of the guiding layer into the substrate and the airspace of an asymmetric slab waveguide caused by periodic refractive-index fluctuations. Also discussed is the effect of backscattering of a guided wave into itself. The periodic index fluctuations may be caused by an acoustic surface wave. For this reason, we assume that the intensity of the index fluctuations decreases exponentially with increasing depth below the surface of the guide. However, out discussion is general, and the acoustic surface wave is used only as an example. Numerical results and graphic examples are given.