Absolute Band Gaps Of Two-Dimensional Square-Lattice Photonic Crystal With Taiji-Shaped Dielectric Rods

Photonic crystal (PC) is a novel type of artificial periodic material, of which themost important property is photonic band gap (PBG) which can forbid the light incertain frequency region. In recent years, the researches on photonic crystal havedeveloped rapidly due to the novel properties and potential applications of photoniccrystal. The further research of photonic crystal will improve the development ofphotonics and optical communication industry. In our article, we mainly constructeda novel type of two-dimensional (2D) square-lattice photonic crystal (SLPC) withTaiji-shaped dielectric rods (TSDRs) and analyzed the properties of PBG in theangle of scatterer’s symmetry. The main results are given as follows:Firstly, we constructed a new type of2D SLPC with TSDRs, of which thescatterer’s symmetry was quite poor, and then analyzed the properties of PBG byPlane Wave Expansion Method (PWM). By comparing the absolute PBG withanother three types of PCs with different scatterer’s symmetries (circle, button,semicircle and Taiji) at the same filling ratio, we find that both the number and widthof absolute PBG significantly increase with the reducing of scatterer’s symmetry.The corresponding physical explanation was also given in the angle of bandsdegeneracies. The results show that the reduction of scatterer’s symmetry can breakbands degeneracies at high symmetry points of the first Brillouin zone, and thenproduce an effective increase in the number of absolute PBG and a broadening inabsolute PBG width.Secondly, we analyzed the influence of dielectric constant contrast and threegeometric parameters of button-shaped scatterer R、r and on the absolute PBG in2D SLPC with button-shaped dielectric rods. Results show that all these parameterscan affect the absolute PBG in some different extents. After optimized calculation,we can obtain the largest PBG with the width0.0638a/2c and at most fiveabsolute PBG.Finally, we analyzed the effect of dielectric constant contrast and threegeometric parameters of Taiji-shaped scatterer R、r and on the absolute PBG in2DSLPC with TSDRs. Results show that all these parameters can affect the absolute PBG in some different extents. After optimized calculation, we can obtain the largestPBG with the width0.0485a/2c and at most nine absolute PBGs.