Sensitivity enhancement of surface plasmon resonance sensor employing 2D black phosphorus: an analytical insight

Surface Plasmon Resonance (SPR) sensors play a pivotal role in real-time, fast response, and label-free detection of molecular interactions. However, achieving high sensitivity and precision remains a key challenge. In this study, an optimized sensor structure composed of CaF2/Ag (50 nm)/BP (5 layers) has been proposed using the Transfer Matrix Method (TMM). The proposed sensor exhibits an enhanced sensitivity of 464°/RIU, a detection accuracy of 0.49, and a quality factor of 98.09 RIU-1, within a refractive index range of 1.330 to 1.335. The enhanced sensitivity is attributed to the use of 2D black phosphorus (BP), which has exceptional light-matter interaction and tunable optical properties. The achieved penetration depth (PD) of approximately 189 nm ensures strong confinement of the evanescent field near the sensing interface, enabling enhanced biomolecular detection. These findings indicate that BP-based SPR sensors hold significant promise for next-generation optical sensing technologies, with potential applications in medical diagnostics, food safety, and environmental monitoring.