Split Ring Resonator-Based Multimode Plasmonic Optical Biosensors for Comprehensive Antigen Detection

In this work, a comprehensive investigation and analysis of a novel plasmonic multi-mode refractive index (MMRI) optical biosensor is presented, utilizing split ring resonators (SRRs) for detecting hemoglobin concentration and prostate-specific antigen (PSA). The biosensor structure is accurately modeled using the finite difference time domain (FDTD) numerical solution method. By examining the materials and dimensional parameters, we identify that the biosensor design supports five resonance modes within the reflection spectrum ranging from 700 to 1200 nm. All five modes exhibit acceptable performance; however, mode 2 exhibits the highest sensitivity and figure of merit (FOM) among the resonance modes, with sensitivity measured at 361 nm/RIU and an FOM of 97.5 1/RIU, representing an excellent outcome. Additionally, Resonance Mode 5 demonstrates commendable performance, with sensitivity values of 225 nm/RIU and an FOM of 80.5 1/RIU. These findings highlight the effectiveness of the biosensor design, particularly in utilizing multiple resonance modes to enhance detection capabilities.The study highlights that elevated PSA levels are linked to prostate cancer, while high hemoglobin concentration is associated with conditions like polycythemia. Therefore, mode 5 is selected for detecting PSA concentration, and mode 2 is chosen for detecting hemoglobin concentration. This dual-mode detection capability and the optimization of resonance modes for specific biomarkers represent significant advancements in the design and functionality of optical biosensors.