Single scatterer Fano resonances in solid core photonic band gap fibers

Solid core photonic bandgap fibers (SC-PBGFs) consisting of an array of high index cylinders in a low index background and a low index defect core have been treated as a cylindrical analog of the planar anti-resonant reflecting optical waveguide (ARROW). We consider a limiting case of this model in which the cylinders in the SC-PBGF cladding are widely spaced apart, so that the SC-PBGF modal loss characteristics should resemble the antiresonant scattering properties of a single cylinder. We find that for glancing incidence, the single cylinder scattering resonances are Fano resonances, and these Fano resonances do in fact appear in the loss spectra of SC-PBGFs. We apply our analysis to enhance the core design of SC-PBGFs, specifically with an eye towards improving the mode confinement in the fundamental bandgap.