Highly increased photonic band gaps in silica/air structures

We explore the possibilities of achieving larger out-of-plane band gaps in two-dimensional silica/air photonic crystals with hexagonal symmetry. By modification of the basic hexagonal unit-cell, we demonstrate a new photonic crystal structure, for which the size of the band gaps is increased several times compared to those of simple hexagonal structures. The new structure allows design of silica/air photonic crystals exhibiting complete out-of-plane two-dimensional photonic band gaps for realistic fabrication parameters. We propose a new design of photonic crystal fibers based on the modified hexagonal structure. The advantages of the new design over recently fabricated photonic crystal fibers are discussed, and a calculation of a guided mode, localized at a low-index core region, is presented. (C) 1998 Elsevier Science B.V. All rights reserved.