Study On Properties Of Slow-light And The Design Of Novel Two Dimensional Photonic Crystal Waveguide

Slow light can be used to enhance the interaction between light and matter,it has important applications in various fields such as optical buffer,optical communication and nonlinear optics.Among many slow light generation technologies,slow light based on photonic crystal waveguide(PCW)has attracted people,s attention because it is widely used in optical communication recently.However,the slow light with high group refractive index produced by defect waveguide is often associated with large group velocity dispersion,which severely limits the bandwidth,resulting in distortion of the optical signal,affecting its application in practice.To solve some main problems of the slow light waveguide,such as large GVD,narrow bandwidth and high loss,we have studied several methods to optimize slow light in our paper.We have made simulations through plane waveguide expansion method and finite difference time domain method,and the simulation results have been analyzed in detail.Eventually,slow light with low group velocity,high group index and low GVD is realized.Details are as follows:1.A brief introduction on the concept of slow light and some methods of generating slow light are given.The generation mechanism and parameters of PCW slow light are described.The calculation principles of two methods–PWE and FDTD of PCW slow light have been shown here,and a detailed description of these two methods in calculating the waveguide dispersion curve is given.In addition,the research statuses of the photonic crystal slow light waveguide are summarized.2.We have carried out comparison and analysis of the square lattice photonic crystal waveguides with round silicon pillar and the triangular lattice photonic crystal waveguides with air holes.It is found that the former has lower group velocity when reducing the radius of a row of media column.The effect of defect column radius of the square lattice PCW with round silicon pillar on the slow light properties has been studied.It is found that the group velocity decreases and the bandwidth narrows with the increase of the column defects radius.The influences of the defect air holes on slow light properties are also discussed when rd >0.3a and rd <0.3a.It is found that the maximum group velocity will decrease with the increasing defect air holes radius.The energy transmission of light with different frequencies in the slow light waveguide is given.At last,it is shown that the PCW with triangular lattice Si-based air holes has superiority over that with square lattice in producing slow light.3.Based on the triangular lattice Si-based air holes PCW,by changing the position of air holes along the direction paralleling to the waveguide,slow light with group index of 31 and bandwidth of 19.1 nm has been obtained firstly.Secondly,by embedding the slot in the waveguide,then moving air holes along the direction perpendicular to the waveguide,slow light with group index of 30 and bandwidth of 23.6 nm has been obtained.Finally,by changing round air holes to elliptical air holes,slow light with group velocity of 22.7~35.7 and bandwidth of 16.7 nm has been obtained when constantly adjusting the length of the major axis and minor axis of the elliptical air holes.