Resonances of asymmetric dielectric waveguides containing a diffraction grating

Guided-wave resonances in periodically modulated asymmetric dielectric waveguides are studied by means of the rigorous coupled-wave theory. The resonances in the i=-1 order wave amplitudes evaluated at z=0 and z=d/ Lambda (where d/ Lambda =5) are shown as a function of the external angle of incidence. The waveguide is asymmetric with epsilon /sub 1/=1, epsilon /sub 0/=2, epsilon /sub 3/=1.9, and a modulation index of Delta epsilon / epsilon /sub 0/=0.005/sub ./ The resonant wave amplitudes at the two interfaces are well separated due to the asymmetry of the waveguide. It is shown how the resonances couple to the propagating diffracted waves with adjacent order numbers. A high degree of switching is observed between the transmitted wave, DE/sub 30/, and the reflected one, DE/sub 10/. However, this occurs over a very small angular range of the input wave.<>