Research On Slow Light Properties In Nonlinear Line Defect Photonic Crystal Waveguide

With the development of all-optical network,its core device-all-optical buffer is undoubtedly the most attracting part in the research on optical network.The optical buffer realized by photonic crystal is easy to be practical,which brings a new opportunity for the development of all-optical cache.Due to nonlinear optical materials have high energy gain characteristics,the introduction of nonlinear materials into photonic crystals,to further improve the photon crystal slow light effect,is of great importance for the future of the high-speed and large capacity optical buffer research and development.In this paper,the slow light characteristics of nonlinear line defect photonic crystal waveguides are studied.A nonlinear waveguide with different structural parameters and lattice structure is designed and compared with the slow light performance of linear waveguide.It is found that that the nonlinear line defect photonic crystal waveguide can increase the bandwidth and reduce the dispersion under the small group velocity.The major work and innovation of the paper includes the following.1 The linear material dielectric column in the perfect photonic crystal is replaced by Kerr nonlinear material and the line defect is introduced to form a nonlinear line defect photonic crystal waveguide.Adjust the structural parameters,utilizing finite element analysis of its slow light characteristics.The simulation results show that the adjustment of the structural parameters such as line defect width,dielectric column radius and defect column size can change the waveguide group velocity and find the optimal structure.The group velocity can reach 0.018 times of the vacuum speed.Compared with the linear waveguide,the bandwidth of the nonlinear line defect waveguide is 0.0316 and the group velocity dispersion is [-4.43,2.69]*103 at the group velocity of the same order of magnitude 10-2c,which is 1.5 times higher than that of the linear line defect waveguide,The dispersion is reduced by two orders of magnitude.2 The lattice structure of the nonlinear line defect waveguide is further optimized to improve the slow light performance.The simulation results show that as the distance between the dielectric column and the defect column is reduced and the distance of the defect column is shifted to the left and right,the velocity group of the slow light decreases gradually.When the distance between the dielectric column and the defect column is 0.8a and the defect column is shifted to the left and right by 0.1a,the optimal slow light effect is obtained.Its maximum group velocity is reached 1.2*10-3c,the bandwidth is 0.00026,the group velocity dispersion is [-2.69,1.38]*105,the normalized delay bandwidth product value is 0.2798.3 The low dispersion slow light performance of nonlinear line defect waveguides is analyzed theoretically,and calculate the main performance indicators of slow light buffer.It is found that compared to linear photonic crystal waveguides,the slow light performance of the nonlinear line defective waveguide is better than that of the linear waveguide,which has the dispersion compensation performance and can obtain the low dispersion.The designed waveguide is applied to the optical buffer,the available buffer time is 2777.78 ps,the buffer capacity is 108.33 bit and the buffer bit length is 9.2?m.Therefore,the nonlinear line defect photonic crystal waveguide has very important research value for optical buffer implementation.