Transmission Characteristics Of Silicon-based Microring Resonator And Its Applications

As the feature size of transistor keeps deceasing,the fabrication of large-scale integrated circuits is limited by the basic physical principles,such as quantum tunneling effect.Electrical methods such as reducing the transistor size and improving the working frequency for improving the speed of the information processing has encountered the bottleneck.Meanwhile,with the rapid development of human society,which can be represented by internet of things,higher requirements on the speed and capability of information processing applications such as the Internet,video and big data are highly demanded.In a manner of speaking,the improvement of the electronic information processing performance is approaching bottleneck and better performance for information processing are required by people,and this contradiction has been become a main problem faced by researchers.Since silicon on insulator material(SOI,Silicon on Insulator)has high refractive index,strong ability to limit the C-band light,compatibility with CMOS(Complementary-MetalOxide-Semiconductor)technology and other advantages,it has become the ideal material for optoelectronic devices.In recent years,the rapid development of integrated optics based on SOI materials inherited the development and ideas of integrated circuits for decades,and utilizes CMOS technology to achieve compact optical devices.Meanwhile,the photonic devices based on the SOI material can be modulated conveniently due to the plasma dispersion effect and the thermo-optic effect of silicon material,which greatly enriched the device function and scope of application.Microring resonator(MRR),consisting of a closed ring waveguide and a straight waveguide,is an important component of integrated photonic devices based on SOI.Because of its advantages of mature technology,highly integration and the mixed integration between optics and electrics,it is often used to build a variety of integrated optical devices.Transmission characteristics and applications of silicon based MRR were studied in this thesis.Starting from the basic theory,the characteristics of SOI material system,typical micro/nano optical waveguide structures and the basic theories of silicon based micro/nano waveguide(electromagnetic field theory,frequency domain coupled mode theory and time domain coupled mode theory),especially the bending coupling of silicon-based micro/nano optical waveguides,were sorted out and explored.The filtering,switching and time characteristics of Add-Drop MRR were analyzed by the scattering matrix model.The main work includes the following points:1.The fabrication process,test platform and test methods and test steps of silicon-based micro/nano photonic devices were described.The single-mode conditions of silicon-based micro/nano waveguide,the relationship between the radiation loss and the bending radius,and the influence of the coupling coefficient and the coupling face design on the output performance of the device were analyzed.Finally,a set of Add-Drop type MRRs with different coupling gaps and the width of 400 nm,height of 220 nm and the slab's thickness of 90 nm has been designed,fabricated and tested.And the relationship between the coupling distance and the free spectral region,optical bandwidth and quality factor has been obtained,which can provide a reference for the design of tunable Fano resonator,optical half adder and one bit optical digital comparator in the subsequent chapters.2.The mechanism of Fano spectral generation has been described,then a tunable Fano device with simple structure based on MRR was proposed.The resonant spectra generated by the Fano resonant system are fundamentally formed by the coherent optical interference of continuum resonant states and discrete resonant states with a certain phase difference.The working principle of the Fano device and the influence of the structural parameters on the output port of the transmission spectrum were analyzed by using the transfer matrix model.And the tuning principle and tuning scheme of silicon-based photonic devices were also compared and determined.Finally,a Fano resonator with a micro-heater structure were designed on the SOI.The experimental results show that:The Output spectrum of the Fano resonator can be precisely controlled by tuning the driving voltage of the micro-heater.And the extinction ratio of the Fano spectrum is 10.02 dB and the edge drop ratio is 101.3 dB / nm.3.A kind of optical information processing scheme called " direct logic " has been studied,and a optical half adder and a single-bit optical digital comparator were constructed with MRR as switches.Compared with the previous structures,cross waveguide structure and three coupling regions in a single MRR are eliminated in the proposed circuit,which are beneficial to reduce the insertion loss and crosstalk of the device and improve the quality of output signals.The influence of the structural parameters on the output performance of an optical digital comparator has been discussed using the matrix model.As a proof of principle,the thermo-optic effect of silicon is employed to realize the tuning control of optical switch.Its corresponding static spectral characteristics have been analyzed,and the corresponding dynamic results have been obtained successfully.Finally,according to the time characteristics of the MRR switch,the ultimate working speed of the half adder and comparator has been evaluated: If the Q value is 104,the limit working frequency of the device is about 6.7 GHz;And if the Q value is 103,the device's working frequency can reach 67 GHz.