| Compare with established commercial optical bio-sensing techniques such as fluorescence measurements, whispering-gallery-mode(WGM) Optical biosensors have the advantages of label free, high selectivity, compact structure, low cost of integration, high Q factor and so on, so they are of great value in detecting biomolecules at low concentrations in biomedicine, food safety, environmental monitoring and other fields.This thesis focuses on several kinds of WGM biosensors based on different silica-based material and related biosensing performances, aimed for the realization of high-performance label free biosensing technology. The main work of this thesis includes several items as follows.Firstly, the fundamental theory of the WGM resonator is studied including the resonance condition, coupling mechanism of WGM resonator and mode analysis. Several performance parameters such as quality factor(Q factor), extinction ratio(ER) and free spectral range(FSR) were explained, especially for the effect of coupling parameters on the performance of WGM resonators.Secondly, the principles of WGM-based label-free biosensor based on the coupling waveguides are introduced. Micro-ring and micro-disk biosensor are designed and sensing properties are analyzed. Then a novel biosensor with spiral-double-racetrack resonators is proposed and designed, focusing major efforts on the effect of geometry parameters on the sensing performance. Great sensing performances are achieved based on numerical analysis, which shows that it’s of great potential in biosensor research field.Thirdly, the effects of different kinds of noises, such as thermal noise and optical source noise, on the sensing performance are investigated carefully. A differential WGM biosensor array is designed to eliminate noise disturbance and enhance the detection accuracy,and a multi-WGM biosensor array is proposed to achieve multi-channel parallel detection. The benefits are also described.Fourthly, the integrated optofluidic biosensor chip is studied including the immunity theory and the biological modification principle. The benefits of microfluidic channels to form biosensor chips are described. Then based on the principle theory of molecular adsorption and mass transport in dilute solutions, simulations of molecular adsorption on the surface of the WGM micro-cavity are carried out by using multidiscipline coupled-field analysis method. The influence of the microfluidic channels and the flow property on the adsorptive action are discussed. Microfluidic channels including single, dual and multiple channels are designed to form the transport and delivery system of an integrated optofluidic biosensor chip.Finally, the fabrication technology of WGM resonator and microfluidic channel is presented. Then a WGM microdisk biosensor with PDMS microfluidic channel is designed and fabricated and the sensing performance is measured. |
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