Research On Silicon-based Integrated Microwave Photonic Signal Processing

Microwave photonics,which combines microwave engineering and photonics technology,has the advantages of large bandwidth,low loss and immunity to electromagnetic interference,and has broad application prospects in high and new technology fields such as communication networks,remote sensing and national defense.With the continuous emergence of new information technologies such as 5G/6G communications,Internet of Things,cloud computing,and virtual reality,there has been a significant surge in the demand for network capacity in various industries.Traditional microwave photonic systems based on discrete devices and specific applications are facing scientific and technical issues as well as severe challenges in terms of bandwidth,energy consumption,system reliability and stability.Thanks to the development of integrated photonics technology and the maturity of photonic chip manufacturing process,integrated microwave photonics enables the minimization of the system,providing smaller size,better stability,lower cost,larger reconfigurability and higher integration level for future advanced communication systems,which is an inevitable trend for microwave photonic systems to be truly practical.Unlike the relatively single material platform of integrated circuits,photonic integrated circuits can be realized in rather diverse material platforms such as silicon-on-insulator,silicon nitride,doped silica,III-V materials,lithium niobate,and polymers.The appropriate material platform can be selected according to different application requirements.Among them,the fabrication process of silicon-based photonic devices is compatible with the mature CMOS technology that SOI platform is quite promising to realize large-scale integration and hybrid integration with electronics.Research in this dissertation is based on silicon photonic platform,where microring resonators and MZIs are employed as fundamental devices.Aiming at current problems in integrated microwave photonics,high-performance and on-chip integrated microwave photonic systems are designed and fabricated to implement different microwave signal processing functions.Specific achievements and contributions can be summarized in the following aspects:(1)A highly integrated reconfigurable and tunable microwave photonic filter is proposed and fabricated.By optimizing the structural parameters of the microring resonator,an on-chip microwave photonic bandpass filter based on a phase modulator,four cascaded high-Q microrings and a photodetector is designed.By adjusting the voltage of the thermal electrode on the microring,the reconfigurable passband bandwidth ranging0.22～0.54 GHz and the tunable central frequency ranging 6.1～35.9 GHz can be realized simultaneously.Further studies involving system filtering characteristics and RF link performance are also performed.(2)A highly integrated dual-modality microwave frequency measurement system is proposed and fabricated.Aiming at the problems of single-function and discrete system of the current microwave frequency measurement systems,an on-chip dual-modality microwave frequency measurement system including a silicon-based modulator and a silicon-germanium photodetector is designed based on high-Q microring resonators and asymmetric MZI.Based on the frequency-power mapping scheme,the system can identify different types of multi-frequency microwave signals.Based on the frequency-time mapping scheme,it can dynamically monitor the instantaneous change of a single frequency.The frequency measurement range is 10～20 GHz,and the resolution is about 1GHz.The functional complexity and integration level of the system have been greatly improved,paving the way for the practical application of integrated microwave photonic systems.(3)A large-scale ultra-wideband reconfigurable photonic analog signal computing chip is proposed and fabricated.Taking a 2×2 MZI as the basic adjustment unit,a3×3-scale reconfigurable on-chip photonic analog signal operator is constructed by using24 MZIs and 52 thermo-optic phase shifters.By optimizing the waveguide network structure,the instantaneous processing bandwidth of each function is larger than 40 GHz.By adjusting the state of the MZI basic unit,different computing functions can be reconfigured and quickly switched between each other.By further altering the voltage parameters of the MZI,the operation order can be tuned.The chip effectively breaks through the limitations of optical analog signal processors in terms of bandwidth and reconfigurable scale,and provides a solution for realizing high-speed and high-efficiency on-chip optical computing.