Design Of Photonic Crystal Filter For Optical Network On Chip

The filter is an important device for wavelength division demultiplexing in the optical network on chip.The traditional electronic filter has large size,low transmittance and high insertion loss,which can not meet the development needs of high integration and high performance of the optical network on chip.As an artificial metamaterial,photonic crystal has small size,high transmittance,low insertion loss and other advantages,which has important application value in optical communication,optical information processing and other fields.In this thesis,in order to improve their transmittance,reduce loss and reduce size,based on the two-dimensional photonic crystal,by constructing different defect structures,designing three different structures of four-channel photonic crystal filters.The research contents of this dissertation are listed as follows:Firstly,four-channel photonic crystal filter based on point-defect microcavities.An ultra-small four-channel photonic crystal filter based on point-defect microcavities is proposed.Based on the resonance coupling principle between point-defect microcavities and line defects,point-defect microcavities and line defects are introduced into the square lattice photonic crystal to form the photonic crystal filter structure.By changing the size of dielectric columns of point defect microcavities,the filter can efficiently output four wavelengths.The transmissivity is above 99%,and the average insertion loss is 0.0253 d B.Due to the use of point defect microcavities,the size of the filter is only 65.93μm².Secondly,four-channel photonic crystal filter based on hexagonal microcavities.A tunable four-channel photonic crystal filter based on hexagonal microcavities is proposed.The structure is based on the triangular lattice photonic crystal,four hexagonal microcavities and four point defect microcavities are cascaded to form the photonic crystal filter.The Si dielectric columns of four hexagonal microcavities are replaced by the phase change material Ge₂Sb₂Se₄Te₁（GSS₄T₁）.The tunable filter wavelength is achieved by heating the GSS₄T₁dielectric column to change the crystal ratio of the material,the refractive index is changed to achieve adjustable output wavelengths.The simulation results show that the device can efficiently output eight optical signals in the range of1310～1500 nm.The transmittance is above 99%,the insertion loss is basically within0.042 d B,and the size is only 74.05μm².Thirdly,four-channel photonic crystal filter based on the hexagonal loop resonator.A four-channel photonic crystal filter based on the hexagonal loop resonator is proposed.Firstly,a hexagonal loop resonator is introduced into the triangular lattice photonic crystal,and then the structure is divided into four regions with different sizes.By introducing four point-defect microcavities in four regions and coupling them to the hexagonal loop resonator,the filter can realize wavelength selection.After parameter adjustment,the transmittance of the structure at 1576.83 nm,1603.38 nm,1550.00 nm,and1626.76 nm is as high as 99%,and the insertion loss is as low as 0.0406 d B.At the same time,only all the dielectric column materials of the filter are replaced by GSS₄T₁,which can realize the purpose of tunable filtering.By using heat treatment to change the crystal proportion of the dielectric column,the refractive index is controlled between 3.46 and 3.5.The tunable filter can efficiently output 20 wavelengths in the range of 1560～1650 nm,the transmittance is above 94.5%,and the insertion loss is less than 0.25d B.Due to the four-channel filtering through only one resonator,the size of the filter is only 110.44μm².In the paper,these designed filters have excellent performance,it has broad application prospects in the field of wavelength division demultiplexing of optical network on chip.