Silica-air photonic crystal fiber design that permits waveguiding by a true photonic bandgap effect.

A theoretical investigation of a novel type of optical fiber is presented. The operation of the fiber relies entirely on wave guidance through the photonic bandgap effect and not on total internal reflection, thereby distinguishing that fiber from all other known fibers, including recently studied photonic crystal fibers. The novel fiber has a central low-index core region and a cladding consisting of a silica background material with air holes situated within a honeycomb lattice structure. We show the existence of photonic bandgaps for the silica–air cladding structure and demonstrate how light can be guided at the central low-index core region for a well-defined frequency that falls inside the photonic bandgap region of the cladding structure.