Microring-based Electro-optical Modulator For Photonic RF Front-end

The electro-optic modulator is the core unit for the conversion of microwave signal to optical domain in the photonic rf front end.In order to satisfy the dynamic optical transmission of the whole communication link,large modulation bandwidth and high performance electro-optic modulator are needed.The high performance electronic information system is highly sensitive to electromagnetic signals due to its susceptibility to electromagnetic weapons or transient electromagnetic pulses.To solve this problem,we put forward the micro ring resonator optical waveguide was used to construct from electrode electro-optic modulator,and use the full dielectric resonance antenna to enhance the field of microwave signals,by dielectric antenna and micro ring modulator optical waveguide mode field matching,microwave light modulation and photonic rf receive front end,in order to promote the communication system of electromagnetic mutilate provides a possible effective way.In this paper,the electro-optic modulator based on single crystal Lithium niobate film material(LNOI)on silicon substrate is mainly studied for the electro-optic conversion of photonic rf front-end.The main research work is as follows:(1)The optical input-output waveguide grating coupler is designed for the optical waveguide microring resonator,and computer simulation verification is completed.On the basis of Bragg phase matching condition,coupling efficiency calculation method,and finite-difference time domain method(FDTD),two grating couplers with uniform and non-uniform structures are designed on the LNOI waveguide structure.Eigen equations based on coupled mode theory and coupling efficiency was deduced and grating period,duty cycle and the relationship between etching depth,and by using FDTD simulation and verification analysis,applying the ideas of the control variables in the wavelength of 1550 nm TM polarization mode,etching depth is 350 nm,grating period is 980 nm,duty ratio is 0.37 when the coupling efficiency of 35%,rather than the uniform grating in the case of the etching depth unchanged,by adjusting the cycles of linear change rate,analyzed the structure of two kinds of grating coupler properties of TM mode under polarized light.(2)The structure optimization of the optical waveguide microring resonator facing the Ku band 12.8GHz RF front end was completed.In order to improve the electro-optical modulation efficiency of microrings,the width of LN waveguide and the relationship between the coupling region and the coupling coefficient are optimized and designed at the frequency of 12.8GHz of rf signal,and the coupling coefficient and the length of the coupling region are designed at the high Q value of 10~6.Through theoretical derivation and simulation,an effective matching scheme between the resonant field of dielectric resonant antenna and the resonant field of optical waveguide microring is obtained to realize the coupling conversion between the optical wave field and the microwave.The overall chip design of the microring resonator with asymmetric polarization and the microring structure design based on non-uniform field modulation are completed and compared.(3)The module integration scheme of dielectric antenna and optical waveguide microring electro-optic modulator is designed.According to the field mode distribution characteristics of the hemispherical dielectric antenna and the square dielectric block,the combination and module integration scheme of the dielectric antenna and the optical waveguide microring resonator are designed to improve the modulation efficiency of the lithium niobate electro-optical modulator.