Investigation Of EIT-like Spectrum And Sensing Characteristics Of Optical Micro-ring Cavity

In the research of integrated optical waveguides,the microring resonator attracts more and more researchers' attention due to its small size,simple structure,easy integration and high Q.It plays an important role in the application of optical integrated devices such as optical filters,optical delay devices and lasers,at the same time,the high-Q optical microring resonator has the sensing characteristic of high sensitivity and large detection range.With the realization of various structures of microring resonator,theoretical researches on the electromagnetically induced transparency(EIT)-like and sensing characteristics of the micro-ring resonator are also gradually perfected.Experimentally,in order to obtain the ideal EIT-like spectrum,we usually adjust the parameters of the microring resonator.Therefore,it is significance to theoretically discuss the parameters in the microring resonator for the EIT-like spectrum.On the other hand,with the development of biochemistry,the demand for high sensitivity and large detection range of microring sensors has been further improved.In this paper,we study the EIT-like and sensing characteristics of microring resonator based on coupled mode theory and signal flow theory.On the one hand,considering the asymmetric coupling factor and the applied gain,we studied the asymmetric waveguide four-microring coupling system,and discussed the influence of the parameters on the transmission spectrum of the system by changing the parameters.On the other hand,we explore the physical mechanism with new sensors.Firstly,we established a new theoretical model of microring resonator.Secondly,we focus on the sensing properties of the two sensors(high sensitivity and large detection range)of the microring resonator system.we also analyze various factors that affect the system's effective refractive index and transmission spectral characteristics.Finally,we use FDTD simulation software to simulate our theoretical results.The details are as follows:In the first part,we introduce the research background and application of optical micro-ring cavity,and focus on the EIT-like phenomena and sensing characteristics of the microring coupling system.This includes the classification of microring resonator,research methods of microring resonator,single microring resonant cavity transfer matrix parametric models,and several applications of microring resonators in integrated optics.In the second part,we study the effect of the microring loss and the coupling transfer coefficient on the asymmetric waveguide four-microring coupling system.Based on the coupled mode theory,we obtain the transmission spectrum of the system.By adjusting the parameters,the output port achieve a better EIT-like spectral line-shape.In the third part,We analyzed the feedback embedded dual-microring coupling system and achieved high-sensitivity sensing by introducing a feedback waveguide between the two coupling regions.The transmission spectrum of the system is obtained based on the coupling mode theory.We also discussed the influence of the transmission loss and the coupling coefficient on the sensing characteristics of the system.In the fourth chapter,Based on the vernier effect,we study the change of the transmission spectrum of the output port when the concentration of the analyte in the sensing window changes.Contrasting to the traditional cascaded dual-microring system,we retain the high sensitivity of the sensor and achieve a large detection range.In the last part,we summarize the conclusion of this paper and put forward the prospect of research on the micro-ring resonator.