Design and optimization of planar plasmonic nano-slit gratings for scalable refractive index sensing in visible–near-IR spectra

This study explores the design and optimization of a planar plasmonic nano-slit array for scalable high-sensitivity refractive index sensing in the visible–near infrared (Vis-NIR) spectrum. This functionality arises from the excitation of surface plasmons (SPs) at the metal–dielectric interface, whose resonance position is acutely sensitive to minute variations in the refractive index (RI) of the adjacent medium. While many sensors report higher sensitivities, they often suffer from complex designs or multilayer architectures, which limit their practical viability and scalable production. Addressing this critical trade-off, the optimized geometry yields a high sensitivity of 458 nm/RIU, establishing an optimal balance between competitive performance and structural simplicity for scalable fabrication. Parametric analysis confirms that the sensitivity scales linearly with periodicity across the tested spectral range, while the figure of merit (FOM) is maximized at a periodicity of P =500nm, providing a clear design rule for efficient sensor fabrication.