Study Of Sililcon-based Integrated Microwave Photonic Filter

With the rapid development of wireless communication technology,in order to meet the demand of communication capacity,the wireless communications will be extended to high frequency microwave band.However,the electronic devices have some difficulties in the transmission and processing of high frequency signals,such as the loss of coaxial cable is too large and the sampling rate is limited.Meanwhile,Compared with electronic devices,the optical devices have many advantages in processing the signals with high frequency,such as large bandwidth,low transmission loss,strong immunity to electromagnetic interference,etc.As an important part of microwave signal processing system,the microwave photonic filter(MPF)is proposed to process microwave signals by using optical devices.Therefore,it exhibits superior advangages over the electronic filter.In the thesis,MPF based on microring resonator(MRR),microdisk resonator(MDR)and Mach-Zehnder interferometer(MZI)are studied,the MPF with narrow bandwidth and ultrahigh peak rejection is implemented by using MRR-MZI and MDR-MZI structure respectively.The Fano resonance is also achieved based on the interference between two add-drop MRR.The contributions of the thesis are list as follows:(1)The model of MPF is established through the theoretical derivation of modulation and detection,and the MPF realized by using the amplitude or phase characteristic of some typical optical elements are introduced.Then the theory of MRR is also introduced,because it is the key element used in this thesis.The amplitude response and phase response of MRR are derived by the transfer matrix method.Several important parameters of MRR including extinction ratio,bandwidth and insertion loss are analyzed,which is important for using MRR to realize microwave photonic filter.(2)The MPF with ultra-high peak rejection and narrow bandwidth is realized by using silicon-based under-coupled MRR and the cascade tunable MZI structure.The feasibility of MPF based on MRR-MZI structure is also theoretically and experimentally demonstrated.The influence of intrinsic splitting ratio of MMI on the tunable splitting ratio of MZI is analyzed,as well as the influence of MRR's coupling state on the insertion loss of the MPF.(3)A scheme based on MDR is proposed to reduce the bandwidth of the MPF,and its theoretical analysis and experimental research are performed.In order to get a narrower bandwidth of MPF,the MDR is used in the MPF instead of MRR because the Q of MDR is higher than that of MRR.Meanwhile,cascaded tunable MZIs are used to improve the peak rejection.Therefore,a MPF with narrow bandwidth and ultrahigh peak rejection is realized.(4)Fano resonance with high and tunable slope is realized by using two MRRs combined with cascaded tunable MZI structure.The high slope and tunability of slope and central frequency are implemented in the experiment.The possibility of improving the steepness of the bandpass filter by the Fano resonance is disscussed.