| Due to the compatibility with standard CMOS platform, planar microring resonator with high quality factor can be fabricated at low cost. Based on planar waveguides, it not only allows surface chemical modifications, but can also be integrated with other optoelectronic devices and microfluidic handling, leading to highly integrated and intelligent sensing chips. Furthermore, it offers a unique advantage of reducing the device size without sacrificing the sensitivity by virtue of the resonance. Therefore, micoring resonator biosensor is highly sensitive that can detect minute amount of analytes. Supported by the National Science Foundation of China, the theoretical model and sensitivity are systematically studied in this thesis. The main contents are listed as follows:(1) The coupling property of the bent-straight coupler is thoroughly investigated, based on coupled mode theory and FDTD method. Theoretical method is established, from which expressions of key parameters such as FSR and Q factor are derived.(2) The overall sensitivity of the device is divided into two contributions: waveguide sensitivity and device sensitivity. The relations of device sensitivity and transmission coefficientσ, self coupling coefficient t, and operating wavelengthλare studied, based on which a design and optimization guideline is summarized.(3) By approximating the original Lorentzian lineshape with a Gaussian function, an explicit relation between the quality factor and the device sensitivity is studied. The detection limit is thereafter derived through the quality factor and signal-to-noise ratio (SNR), which is in good agreement with experimental results and universal for microring resonator sensors based on intensity variation.(4) The overall response is derived, with the phase noise of laser source taken into account. The influence of laser linewidth on the overall performance is studied. |
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