Leak loss analysis of slab-type waveguides consisting of two-dimensional photonic crystal

Summary form only. Two-dimensional (2D) photonic crystals (PCs) are promising for extremely miniaturized planar optical devices and circuits. So far, several theoretical studies based on the 2D structure with infinite thickness have been done. Recently, 2D structures with finite thickness have been treated theoretically by introducing the concept of a "light cone". This concept gives us a design-criterion about propagation modes in the cone. However, modes out of the cone have not been treated qualitatively as well as quantitatively, presuming them to be leaky modes. In accordance with the increasing experiments of the 2D structures with finite thickness, successful measurements of transmission/reflection characteristics for the modes out of the cone made it difficult to count on the light cone model for qualitative as well as quantitative physical interpretations of such modes. In this paper, we proposed a novel analytical method applicable for studying modes out of the cone by introducing the concept of leaky terms outside the expanded light cone.