Abstract
Gyroid is a type of three-dimensional chiral structure that has been found in many insect species. Due to the periodic and chiral structure, the gyroid has been shown to exhibit photonic band gap and circular polarization dependent characteristics. Previous results show that the optical properties of the double gyroid can be tuned by refractive index contrast of the constituent materials or the volume fraction. However, double gyroid structures are mainly studied based on one constituent material, either dielectric or metal. The influence of different materials on the optical properties of double gyroid has not been explored. In this work, we investigate the polarization-dependent characteristics of a hybrid metal/dielectric double gyroid based on finite-difference time domain (FDTD) method. The corresponding band structure, transmission spectra, CD indices and coupling indices are calculated to examine the existence of polarization band gap and complete band gap in a metal/dielectric double gyroid. The evolution of band gaps with respect to different fractions of the hybrid system are presented. Furthermore, the dispersion surfaces and equifrequency contours (EFCs) are analyzed in the hybrid double gyroid. Based on the dispersion characteristics, anomalous guiding characteristics including negative refraction and collimation effect are discussed. These results could be of great interests for the design of function of circular-polarization devices based on hybrid metal/dielectric double gyroid structures.