Slow Light Properties Research In Photonic Crystals

Slow light technology is the key part of the light cache, and the optical buffer is key technologies to achieve full optical communications. After the photonic crystals have been proposed, with its unique micro-structure, room temperature operation, flexible design, it show great advantage in terms of slow light with low loss, and unique band gap structure and controllability. In this paper, the slow light of two-dimensional photonic crystal of air ring was studied.This article focuses on the characteristics of band gap and slow light properties of air ring type two-dimensional photonic crystal. After the analysised of energy band dispersion group velocity characteristics of air ring photonic crystal wire waveguide and coplanar waveguide, we designed a new asymmetric photonic crystal line defect waveguide, With optimizing the structure parameters, It is verified that the asymmetric structure has good broadband slow light effect.Air ring photonic crystal object being studied, the main work was done as follows:Firstly, Matlab program of Plane Wave Expansion method (PWE)with supercell was prepared. The energy band structure of the air holes and the medium columnar photonic crystals were analyzed.By modifying program so that it can be applied to analyze the band characteristics of air ring photonic crystal. Various structural parameters on the air band characteristics of photonic crystal ring were analysed.Secondly, the symmetrical of the line defect waveguides and waveguide coupled cavity symmetrical structure were designed. When the ratio of the air inside and outside the ring radius is between 0.15 to 0.35, the better broadband slow light can be achieved in line defect waveguide。Finally, a new type of asymmetric wire waveguide structure was designed. the relevant parameters of the structure were analyzed and optimized. The results showed that:asymmetric waveguide group velocity of light can be reduced to 0.0086c (c is the speed of light in vacuum), and the effective bandwidth is 6.588nm. Normalized delay-bandwidth product can measure the slow light of different type waveguide structure. Data analysis showed that the asymmetric waveguide designed in this paper has good broadband slow light effect.