Research On Slow Light Properties In Nonlinear Photonic Crystal Ring-shaped Cavity Waveguide

All-optical buffering,all-optical delay lines and other technologies are the key technologies for achieving"all-optical networks."The use of photonic crystals to achieve the slow speed of light provides novel opportunities for the realization and development of all-optical buffering and all-optical signal processing.The advantage of slow light in photonic crystal lies in its small size,large bandwidth,and can realize slow light at room temperature.The introduction of nonlinear materials in photonic crystals can achieve better slow light effects due to their high energy gain characteristics,which is of great significance for further development of optical buffers and all-optical networks.In this paper,the nonlinear ring-shaped cavity line defect waveguide and two novel coupled cavity waveguides are designed.In the line defect waveguide design,the slow light performance of both the triangular lattice and the square lattice was compared,and it was found that the square lattice structure was better,and further optimization of the square lattice line defect waveguide structure resulted in high quality slow light.Under the same structure,the slow-light characteristics of the non-linear and linear,ring-shaped cavity and circular-shaped cavity line defect waveguides are compared,and the advantage of slow-light in a nonlinear ring-shaped cavity line defect waveguide is obtained.In order to further reduce the group velocity and increase the bandwidth,two novel types of coupled-cavity waveguide structures,ie,non-linear ring and ring-circular,are designed and constructed.The structural parameters are optimized,and a high-quality slow light waveguide with lower dispersion and wider bandwidth than line defect waveguide is obtained.The relationship between the characteristics of slow light and the ratio of inner and outer radius of the ring was analyzed and verified.The two types of slow-light coupled-cavity waveguides were compared.The innovations in this paper are as follows:1.By optimizing the design,when the ring-shaped and circular-shaped cavity line defect waveguides at the same group velocity,the ring-shaped cavity waveguide has a bandwidth nearly 1.5 times that of the circular-shaped cavity waveguide,and the dispersion also decreases.The ring-shaped cavity waveguide has better slow-light characteristics than the circular-shaped cavity waveguide,and uses less material and reduces cost.2.A novel type of nonlinear ring-circular-shaped coupled cavity waveguide is designed.By optimizing the outer radius and inner radius of the ring,the best slow light effect is obtained when the outer radius and the inner radius are 0.305a and0.149a,respectively.At this time,the group velocity is1.44?10^-4c,and the corresponding bandwidth is.10?10^-5,a slow light waveguide with low group velocity and high bandwidth is obtained,and the stability is good.3.Through the analysis,it is found that the ratio of the inner and outer radiuses of the ring of the coupled-cavity waveguide affects the slow light performance,and the size of the two are important factors as well;when the ratio is fixed,there is a group of optimal outer radius and inner of ring;The slow light waveguide can be optimized by usingR₂/R₁as a new change parameter,and the optimal ratio of inner to outer radius of the ring can be obtained.This research method provides a guide for the study of photonic crystal slow optical waveguides.