Imaging And Coupling In Parallel Multimode Dielectric Slab Waveguides

An extension of a recently developed hybrid technique for computing beam propagation in multimode dielectric waveguides is used to treat coupling between two identical parallel slab waveguides. Propagation on these slabs can be described by system (or normal) modes, which are symmetric or antisymmetric combinations of single slab modes. These two groups of modes possess slightly different self-imaging properties which can eventually result in virtually complete power transfer from one guide to the other. Whether or not the resulting beam in the second guide is well-focused depends on the relation of the coupling distance to the self-imaging distance, as well as the properties of the beam itself.