Linear waveguides in photonic-crystal slabs

Linear waveguides in photonic-crystal slabs, two-dimensionally periodic die lectric structures of finite height, are fundamentally different from waveg uides in two-dimensional photonic crystals. The most important distinctions arise from the fact that photonic-crystal slab waveguides must be index-co nfined in the vertical direction (while a band gap confines them horizontal ly). We present a systematic analysis of different families of waveguides i n photonic-crystal slabs, and illustrate the considerations that must be ap plied to achieve single-mode guided bands in these systems. In this way, th e unusual features of photonic-crystal waveguides can be realized in three dimensions without the fabrication complexity required by photonic crystals with complete three-dimensional band gaps.