SPR sensor based on sapphire prism coupling with dual-Au-layer sandwiched GaN structure for enhanced sensitivity and FOM

Surface plasmon resonance (SPR) sensors are currently applied in various fields, driving the development of precise detection technologies. However, few designs effectively balance ease of fabrication, high detection performance, and structural stability. To address this challenge, we developed an SPR sensor with a sapphire prism-Au/Gallium Nitride (GaN)/Au composite film structure. The GaN thin film enhances sensitivity, while the coupling between the dual Au layers and sapphire reduces the full width at half maximum (FWHM) and improves sensor stability. Simulation results indicate a significant increase in the electric field intensity at the sensor surface. Experimental results demonstrate that the structure exhibits excellent long-term stability. Compared with conventional Au film sapphire prism SPR sensors, this design achieves a 3.14-fold increase in sensitivity and a 5.43-fold improvement in the figure of merit (FOM). This study presents a novel approach to further enhancing SPR sensor performance and highlights the potential applications of this structure in detection technologies.