Radiation losses of waveguide-based two-dimensional photonic crystals:: Positive role of the substrate

Radiation losses occurring in photonic crystals etched into planar waveguides are analyzed using a first-order perturbation approximation. Assuming the incoherent scattering limit, the model indicates that losses diminish as the cladding index approaches the core index. A simple scheme is devised to include these losses into purely two-dimensional calculations by using an imaginary index. Such calculations are shown to agree with corresponding experimental transmission through near-infrared photonic crystals, reproducing the contrasting behavior of the "dielectric" and "air" band edges. (C) 2000 American Institute of Physics. [S0003-6951(00)03205-8].