Trapped photons at a Dirac point: a new horizon for photonic crystals

Optical cavities and waveguides are essential building blocks of many modern optical devices. They rely upon photonic bandgaps, or total internal reflections, to achieve field confinement. Here a new phenomenon is reported of wave localization that is attributable to neither of the above light guiding mechanisms. It is found that what is known as the Dirac point within a photonic band structure can play the role of a photonic bandgap with the establishment of field confinement. The new localized mode occurs at a Dirac frequency that is beyond any complete photonic bandgap, and exhibits a unique algebraic profile. The features of this new wave localization will add new capabilities and more flexibility to the design techniques of novel photonic components and photonic chip architectures