Research On Bandwidth And Dynamic Adjustment In The Two-dimensional Nested Photonic Crystal Coupled-cavity

Since the concept of photonic crystal is brought up,it offers much more and better choices for all-optical buffer device.Due to the unique nano-structure and roomtemperature operation and many other advantages,the optical buffer based on photonic crystal waveguide has captured more and more attention of researchers.In this paper,we research on the slow light characteristic of two-dimensional nested photonic crystal coupled cavity waveguides.Specially,two types of coupled cavities,i.e.,horizontal-,vertical-defect cavity and filled with different concentrations of magnetic fluid in the nested cavity structure.Then,analysing and conparsing the slow light performance.The major works and innovation of the paper include the following.By nesting the photonic crystal lattice with a smaller radius in the perfect photonic crystal lattice,then a empty cell was set in the center to get the point defect twodimensional nested photonic crystal coupled-cavity.To increase the bandwidth,the air holes' positions were changed in both horizontal and vertical directions.The results show: when optimizing the rod position,the group velocity keep with three orders than the speed of the light,and the corresponding normalized delay-bandwidth product(NDBP)values are all more than 0.330.Vertical-defect cavity have the best slow light performance,the relative bandwidth can reach 0.00051 when the group velocity reaches 36.94 10 c-?.Compared with the point defect two-dimensional unnested photonic crystal coupled-cavity,bandwidth increases 0.00017 with the similar velocity.With 0.404 being the highest value achieved when rod is symmetrical shifted to 0.4a in the vertical position.Be filling with different concentrations of magnetic fluid in lattice,which realizes the adjustability of the slow light property.The results show that: as the concentration of filled magnetic fluid increases from 0.25% to 1.75%,bandwidth increased from 0.00051 to 0.00055,increased by 0.00004.When filled with different concentrations of magnetic fluid in different lattices,the bandwidth,group velocity,NDBP values are adjusted continuously as the concentration changes.