Multiplexed biossensors based ok multimode nanoslits

Surface plasmon-based biosensors are widely recognized for their exceptional sensitivity, ease of integration, and versatility across various fields, including biomedical diagnostics, environmental monitoring, and chemical analysis. While these sensors have demonstrated significant potential for real-time, label-free detection, they still face key challenges—one of the most critical being multiplexing. The ability to simultaneously detect multiple biomarkers is particularly important in medical diagnostics, where comprehensive assessments can lead to earlier and more precise disease detection. However, current surface plasmon technologies face limitations in achieving effective multiplexing, underscoring the need for innovative configurations. This thesis presents the design, modeling, fabrication, and experimental validation of a novel surface plasmon resonance (SPR) interferometric biosensor capable of supporting multiplexed detection. The proposed device operates by exciting and interfering counter-propagating surface plasmon waves in a nanoslit structure using optimized grating couplers, achieving high-visibility interference patterns. Full-wave electromagnetic simulations demonstrate a maximum bulk sensitivity of Sb = −3.87W/(m·RIU), a surface sensitivity of Ss = 0.002W/(m·nm), and a resolution down to Rb = 6.3 × 10−6 RIU and Rs = 10 pm, depending on the nanoslit geometry. The optimal grating coupler design reached a total coupling efficiency of 54.7%, ensuring effective SPR excitation with Gaussian beam illumination. To enable multiplexing, a shadowing structure was developed and integrated to allow simultaneous excitation of multiple sensing units with a single expanded Gaussian beam. Simulations confirmed that the device maintains independent sensing responses in each channel with minimal crosstalk. A complete fabrication process, including gold deposition, electron beam lithography, focused ion beam milling, and CYTOP-based microfluidic integration, was implemented. The final device successfully detected refractive index changes in water-glycerol mixtures, experimentally validating the interferometric sensing principle and confirming agreement with theoreticalpredictions. These findings demonstrate that the interferometric SPR platform not only functions as a highly sensitive refractive index sensor, but also offers scalable multiplexing capabilities. This work lays the groundwork for future advancements in three key directions: miniaturizing the optical system for portable diagnostics, functionalizing the sensor for selective biomarker detection, and integrating spatial light modulators for real-time, multi-channel interrogation. Together, these developments promise to enhance the applicability of SPR biosensing in real-world biomedical and clinical diagnostics.