Design And Optimization Of Silicon-Based Microring Biochemical Sensor

With the increasing demand for food and medicine safety, and the growing concern of environmental issues, how to obtain the biochemical sensors which can detect the chemical and biological analyte quickly and accurately has become a research hotspot. Silicon-based microring resonator biochemical sensors not only have high sensitivity and small size, but also are easy to integrate and compatible with the CMOS fabrication. In this thesis, silicon-based microring biochemical sensors were studied.The typical add-drop microring resonator was modeled using the transfer matrix method (TMM), and the numerical simulation of its transmission spectrum has been obtained. The field enhancement factor and the spectral response of critical coupling state were discussed, and various characterization parameters of its response spectrum were analyzed. Besides, by using finite difference time domain method (FDTD), the spectral response was analyzed when pulse injects to this typical structure, and the establishing process of a resonant state in the ring cavity was discussed.Based on analyzing the working principle of the microring biochemical sensor, two of the function-enhanced microring structures (the cascade structure and the microring with waveguide coupled feedback) were modeled and numerical simulated. For the cascade structure, the relation between the coupling coefficient and the spectral width of resonance, the coupling coefficient and the transition of degenerate state to non-degenerate state were analyzed. Besides, the impact of microring cavity’s number and the transmission loss on the transmission spectrum were also discussed. For" the feedback microring, the effects of the feedback waveguide’s length and the coupling coefficient on the output response spectrum were emphatically analyzed. How the two function-enhanced structures improve the characteristics of biochemical sensors was also explained by comparing the performance parameters between the function-enhanced structures and the typical add-drop microring.A novel high-performance optical biochemical sensor based on the Mach-Zehnder interferential effect and the dual-microring resonators with the waveguide-coupled feedback was proposed. The sensitivity of this sensor can be orders of magnitude higher than that of a conventional sensor, and high quality factor is not as critical in it. Moreover, by optimizing the length of the feedback waveguide to be equal to the perimeter of the ring, the measurement range of the proposed sensor is twice as much as that of the conventional sensor in the weak coupling case.