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Abstract:
Label-free, sensitive, and rapid biochemical sensors are increasingly important for a wide range of applications, including early diagnostics and the detection of hazardous gases. Among the most sensitive sensors currently available is the whispering gallery mode (WGM) microtoroid resonator. When combined with the Frequency Locked Optical Whispering Evanescent Resonator (FLOWER) technique and data analysis, this system can detect attomolar protein concentrations within seconds and hazardous gases at part-per-trillion levels.
This dissertation focuses on the development and application of FLOWER. The fundamentals of frequency locking techniques and the experimental setup are detailed. In the first study, the analyte delivery to the microtoroid was visualized to optimize the flow cell structure, and finite element simulation was performed to study analyte collision time, providing insights into the microtoroid's response time at extremely low analyte concentrations. The second study demonstrates the use of FLOWER and the microtoroid to evaluate drug candidates' efficacy against SARS-CoV-2. The final study presents an alternative method for coupling light into the microtoroid using free-space coupling with a single long working distance objective lens. This approach eliminates the need for tapered fiber, offering potential for system deployment outside the lab and enabling multiplexing, which will be thoroughly discussed. Preliminary results supporting these findings are also presented.