Research On Polarization-independent Silicon Waveguide Grating Filter

In recent years,Silicon-On-Insulator(SOI)has been proven as an ideal platform for integrated optics because its high index contrast,which results in strong optical mode confinement,and makes it possible to scale photonic devices to the sub-micrometer level.With the rapid development of silicon-based integrated photonics,scholars have also conducted in-depth research on Bragg waveguide gratings,which have become one of the important devices in silicon-based integrated photonics.The SOI-based grating is more compact.Besides,the manufacturing process is simple and cmos-compatible,which result in mass production,simple process,and lower cost.However,due to the asymmetry of the SOI waveguide cross-section,it also brings polarization-related problems,which has attracted the attention of researchers around the world.Based on the characteristics and theories of SOI waveguide and grating,this paper proposes polarization-independent grating filters and polarization rotators,and verifies them through simulations.The detailed description is followed:(1)A polarization-independent filter based on cascaded gratings on single-mode and multi-mode waveguides is proposed.By optimizing the parameters of the gratings,polarization-independent filtering is realized.The simulation results show that for the designed polarization-independent filter based on cascaded single-mode waveguide gratings,the bandwidths of the TM₀polarization state and TE₀polarization state filter spectrum are21nm and 20nm,respectively,the extinction ratio is the same,and the filter center wavelength deviation is 0.5nm.For the designed polarization-independent filter based on cascaded asymmetric multimode waveguide grating,the bandwidths of the TE₀polarization state and the TM₀polarization state filter spectrum are both 7nm,the extinction ratio is 3d B,and the center wavelength deviation of the filter center is 3nm.(2)A polarization-independent filter based on multimode waveguide asymmetric grating and mode converter is proposed.By optimizing the parameters of the grating and mode converter,polarization-independent filtering is realized.The simulation results show that the center wavelength and bandwidth of the two polarization filter spectrum lines are basically the same,the filter center is 1542nm,the bandwidth is 15nm,and the extinction ratio differs by 0.3d B.The reflected light achieves polarization rotation.In the wavelength range of1536?1547nm,the conversion efficiency of the two polarization states of TE0 mode and TM0mode has reached more than 90%,and the bandwidth is greater than 11nm.