Aperiodic distributed-parameter waveguides for integrated optics

Aperiodic distributed-parameter waveguides are considered for use as reflectors and filters in integrated optics. Coupled-mode theory is used to predict the effects on modal propagation of aperiodic perturbations induced in a slab waveguide. In particular, it is shown that aperiodic perturbations can couple forward-traveling bound modes to backward-traveling bound modes; and that the frequency dependence of such a coupling process can be controlled through the aperiodicity. It is suggested that aperiodic coupling may be used to realize optical-waveguide reflectors and filters having predetermined spectral-response characteristics. As examples, the spectral-response characteristics of a narrow band-stop filter, a broadband-stop filter, and a narrow band-pass filter are calculated and presented.