| This dissertation investigates the optical detection of antigens (in this case, food pathogens such as Salmonella) with fiber-optic immunosensors. The major techniques used for this optical detection include: (1) Linking the antigens to some physical tracers that can be optically detected; (2) Collecting and transmitting the optical signal to an optical detector.; From an optical point of view, the problem is a nonimaging-optics problem to collect a fluorescent signal from an extended Lambertian source and deliver it to an optical detection system with maximum energy transfer and distinct wavelength separation.; A raytrace model of the optical detection system was used for numerical simulations to analyze and optimize the optical design. The result leads to an improvement of the optical detection. Related physical problems such as magnetic focusing effect, fluorescence detection, and wavelength separation have also been studied in detail.; With the adoption of a single-step immunomagnetic assay, experimental studies have been conducted for the detection of Salmonella, with a dual-fiber optical probe and tapered tubular waveguide probes. The test results have shown that the detection system gives detection limit of approximately 106 CFU/ml with dual-fiber optical probes, and 105 CFU/ml with improved tubular waveguide probes.; The system developed for this research project is designed as a cost-effective portable instrument that may be used for field-testing. Rapid and on-site detection, low cost instrumentation and a reusable optical probe have been emphasized throughout the study. |
