Optimizing fiber-optic surface plasmon resonance–based sensors: an exploration of different taper profiles and metal choices for enhanced performance

We thoroughly evaluate four different taper profiles for fiber-optic surface plasmon resonance (SPR) sensors. We utilized the transfer matrix method to these profiles to evaluate their effect on key performance parameters, including sensitivity, figure of merit (FOM), detection accuracy, full-width at half maximum, amplitude dip, and half-power point. With six different metals (Au, Ag, Cu, Al, Ni, and Pt), we found that the sinusoidal taper profile with Au has the maximum sensitivity, reaching 11.9 μm/RIU at a taper ratio (TR) of 5, and a corresponding FOM of 23.36 RIU−1. In comparison, at TR=6, the exponential taper profile using Cu was able to attain a sensitivity of 25.1 μm/RIU. To optimize the sensor for visible to near-infrared applications, the results demonstrate that raising the taper ratio considerably moves the SPR dip toward longer wavelengths (e.g., from 600 to 850 nm for Au). For real-time bio-sensing applications, these findings are crucial in determining the design of high-performance, tunable SPR sensors that can detect minute changes in refractive index.