Light propagation in a photonic-crystal-slab line-defect waveguide

The guided and leaky modes of a photonic-crystal-slab line-defect waveguide were investigated by means of the direct three-dimensional (3-D) finite-difference time-domain (FDTD) simulation. The simulation predicted quasi-guided modes with long lifetimes in the cladding-mode continuum, while quasi-3-D analyses using projected band diagrams revealed only the existence of guided modes outside that continuum. It is shown that the direct 3-D analysis is necessary to account for measured transmission data for the photonic-crystal-slab line-defect waveguide with a finite length.