Coupled Waveguide Polarization Beam Splitter With Periodic Micro-structure

Polarization beam splitter plays an important role in these aspects,such as,optical communication,optical sensing,optical imaging and optical computing.Traditional polarization beam splitter is large in size,and can not meet the needs of high density chips integrated in optical applications,and the cost is expensive.On the other hand,the extinction ratio is not high,and the bandwidth is limited if the size is been shortned.To solve this problem,after we have analyzed the design work of four kinds of usual palrization beam splitter,we put forward a new desgin of polarization beam splitter with periodic micro structure.Based on these,we have designed two coupled polarization beam splitters with periodic micro structure waveguide.The plane wave method were used to calculate the structure parameters and the finite difference time domain method was used to analyse the performance of the polarization beam splitter.The results show that the our design of the polarization beam splitter with periodic structure can effectively reduce the length of the polarizing beam splitter,increase the polarization extinction ratio and increase the bandwidth.The work of this paper is mainly reflected in the following three aspects(1)A new design principle of compact high extinction ratio polarization beam splitter was put forward.After analyzed the splitting principle of the multimode interference structure,Mach Zehnder interferometer instrument structure,directional coupler structure and photonic crystal structure.And the advantages and disadvantages of them in performance were compared.Based on these work,combined with the directional coupling theory and structure of photonic crystal band gap theory,a new design principle of a polarization beam splitter was brought up.The principle can effectively reduce the length of the polarizing beam splitter,increase the polarization extinction ratio and increase the bandwidth.(2)An asymmetric coupled waveguide polarization beam splitter with periodic micro structure was designed.Based on the principle we have mentiond above,the expansion method was used to design the parameters of the polarization beam splitter firstly.Then,the accuracy of the calculation results was verified by using the finite difference time domain method.Finally,the performance of the polarization beam splitter was tested.At last,an ultra compact polarization beam splitter with a coupling length of 3.43 ?m has been obtained with a bandwidth of 180 nm.At 1550 nm,the extinction ratios of TE and TM polarizations are 28 dB and 18 dB,respectively.(3)A symmetric coupled waveguide polarization beam splitter with periodic micro structure was designed.The same methods and principle were used as before,the paramters were designd and the performance were simulated.Then,an ultra compact polarization beam splitter with a coupling length of 4.19 ?m was obtained with a bandwidth of 320 nm.At 1550 nm the extinction ratio of TE and TM polarizations are 40 dB and 20,respectively.Finally,comparison and analysis of the performance for the two polarization beam splitters were made.