Modeling of transmission spectra in photonic bandgap waveguides

Photonic crystal fibers have received much attention recently as they show promise for potential device and transmission fiber applications. They have been broadly classified into two categories depending on the light-guiding mechanism in the core: (1) total internal reflection, and (2) Bragg scattering off multiple layers. The latter has generated significant interest because of the possibility of guiding light in air, hence reducing nonlinearity and loss. In this paper, we show that, in addition to Bragg scattering, the spectral characteristics of a 1D photonic bandgap (PBG) waveguide in which the core index is less than the cladding index are also determined by Fresnel reflections from the first high-index layers surrounding the core. The latter will be referred to as the Fresnel regime.