Effect of Point and Linear Defects on Band-gap Properties in Triangular-Honeycomb Structure Photonic Crystals

Hybrid photonic crystals, namely by combining two lattices to create hybrid lattice geometries, which produce larger photonic band gaps, can effectively improve the performance of photonic devices. In this paper, the photonic band gap of the hybrid-lattice photonic crystal was calculated by considering the point and linear defects in the triangular-honeycomb structure based on the plane wave expansion method. The influence of the sizes of air holes on the photonic band gap was simulated by changing the radius ratio of two kinds of air holes in triangular and honeycomb lattices. Three complete band gaps occurred in the hybrid photonic crystal with the triangular-honeycomb structure with the increase of the radius of the small holes in honeycomb lattices, while the width of the complete band gap decreases gradually. Two kinds of defects (point and linear defects) were introduced and the effect on the optical properties in triangular-honeycomb structure photonic crystals was studied. The results show that the width of the photonic band gap reduced after introducing the linear defect, whereas the point defect kept the width of the band gap and the frequency range of the photonic crystal unchanged. Moreover, the limit of the passing rate of the light wave was reduced, and most of the light wave could be transmitted directly through the linear defect.