Research On Linearity And Microwave Frequency-doubling Employing A Silicon Coupling-modulated Microring Resonator

Silicon-based photonic integration,which can meet the demand for high-speed,low-power,high-density,low-cost and compatibility with the traditional CMOS technology,has become a strategic priority in Europe,USA and other developed countries.As the most important optical communication device,the electro-optic modulator will directly affect the quality of the entire optical communication systems.The linearity of the modulator is one of the most important metrics.A well-designed linear modulator can improve the signal quality in long-distance optical transmission.By utilizing the nonlinearity of the modulator,we can get a RF frequency-doubled signal.Therefore,how to rationally use the double-edged sword of the modulator linearity is a problem worth pondering.In this paper,the main research object is a silicon-based coupling-modulated micro-ring structure.The principle of coupling-modulation is presented and its performance is analyzed by using the transfer matrix method.Based on the transfer matrix,the theoretical model for microwave signal generation is established and its modulation process is analyzed.Meanwhile,the causes and mechanisms of nonlinear distortion at the resonance point are discussed.Next,the design of each component in the silicon electro-optic modulator is introduced.In particular,the designs and simulations of the subwavelength grating coupler,the L-shape high-speed phase shifter and the single-drive double-layer traveling wave electrode are described in detail.The performances of the device are optimized by using Comsol and Lumerical MODE/FDTD Solutions.The thesis finally presents the linearity test and microwave frequency-doubling generation based on this device.First,the static transmission spectrum of the device is tested,revealing the device insertion loss?IL?is¹3.6 dB?³.6 dB on-chip IL and⁵ dB input/output coupling loss?.The optical carrier wavelength is then set at the 3-dB working point near the critical coupling wavelength.The spurious-free dynamic range?SFDR?of the device is measured to be 95.94 dB·Hz^2/3@1GHz according to the two-tone RF input test method.In the microwave frequency doubling test,when the operation wavelength is set at the critical coupling resonance wavelength,it can suppress the carrier as much as possible,and generate the frequency-doubled microwave signal by beating it in the photodiode.In the experiment,when the microwave input power is 5 dBm?10dBm?,the suppression ratio between the second harmonic component and the fundamental component is²0 dB?²9 dB?at the critical-coupling wavelength.These experiments prove that the coupling-modulated micro-ring resonator can have different linearities when the operation point changes,which can be utilized to satisfy various applications for microwave signal processing.