Observation of the Dirac mode guidance in Kagome lattice of photonic crystals

Abstract Conventionally, the behavior of light transmission in optical devices is based on total internal reflection or photonic bandgaps. The Dirac mode is regarded as another guiding mechanism that relies on the zero-density of radiation states around the Dirac point to avoid power leakage and thus achieves field confinement. Unlike conventional light guiding mechanisms, the Dirac mode features a unique algebraic decay profile around the Dirac frequency. In this study, the Dirac mode in the Kagome lattice of photonic crystals (PCs) at a Dirac frequency that is beyond any complete photonic bandgaps is observed, and its features are verified using finite difference time domain analyses. The results indicate that the Dirac mode in the triangular, honeycomb, and two-compound lattices of PCs also occurs in the Kagome lattice and has an extremely high quality factor of 1 . 03 × 1 0 6 . Furthermore, analyses of the Dirac mode serve as a convenient method to control the all-range Dirac frequency by modifying the structural parameters accordingly, thus extending the applications of the Dirac mode in modern integrated optical devices.