Understanding All-Solid Honeycomb Photonic Bandgap Fibers

Plane-wave expansion calculations show that a broad higher-order bandgap can be formed in all-solid honeycomb photonic bandgap fibers, different from fibers based on the typical triangular lattice. Both density of states plots and Bloch-mode field distributions reveal that the higher-order bandgap results from a re-ordering of the linearly polarized modes that form the cladding states, that is, those modes with high azimuthal order have more nodal lines than the cladding structure can support and thus are pushed away to high frequencies.