Photonic Crystal Fibres: A New Calss of Optical Waveguides

Remarkable properties of optical fibers with a high-index core region and sorrounding silica/ air photonic crystal cladding have recently been reported. Here we discuss the physics, the special guiding properties, and the theoretical tools developed for the modeling of these photonic crystal fibers. With an emphasis on the applicational aspects of the fibers, we study their single-mode operation, bending losses, and dispersion properties. While exhibiting certain unique properties, the high-index core photonic crystal fibres share many common features with conventional optical fibers, attributed to an operation based on the well-known mechanism of total internal reflection. Fundamentally different from all high-index core fibers, in this work we demostrate a novel type of optical waveguide, operating truly by the photonic bandgap effect. The novel fiber has an improved photonic crystal cladding and a central low-index ´structural defect along which the light is guided. The novel fiber has several unique features due to its different waveguidance mechanism, including remarkable dispersion properties and the potential to localize part of the guided mode in air regions. The results presented are fundamental in the field of photonic bandgap guidance, and this new class of optical waveguides is, therefore, expected to be of future interest to a large variety of research areas.