Year: 2026
Type: article
Abstract: A highly sensitive plasmonic refractive index (RI) sensor based on a split disc–ring resonator (SDRR) is presented and numerically analyzed. The sensor comprises a split disc surrounded by a split ring, both fabricated on a SiO₂ substrate. This structure supports coupled plasmonic modes, specifically ‘bright’ and ‘dark’ modes, which lead to strong near-field interactions and Fano-type interference. These phenomena enable significant localized electric field enhancement at the metal–analyte interface, rendering the sensor extremely responsive to subtle changes in the analyte’s RI. Systematic optimization of structural parameters, including gap widths, disc and ring radius, and metallic composition, revealed that a silver disc–gold ring configuration provides an optimal trade-off between sensitivity and spectral stability. Numerical simulations performed using the Finite-Difference Time-Domain (FDTD) method validate the sensor’s capability to detect refractive index variations, demonstrating its high responsiveness to subtle biological changes. The simulations yield a maximum sensitivity (S) of 1670 nm/RIU, a figure of merit (FOM) of 3.6 RIU⁻¹, a quality factor of 7.4, and a full width at half maximum (FWHM) of 452.8 nm across a refractive index range of 1.33 to 1.53, exhibiting excellent linearity (R² = 0.99983). Owing to its simple geometry, strong field confinement, and tunable metal composition, the SDRR offers a versatile platform for practical biomedical and environmental sensing—such as biomolecule, cancer cell, virus, and bacterial detection. These findings highlight the potential of SDRR-based plasmonic sensors as highly reliable and high-performance devices for next-generation biosensing and environmental monitoring systems.
Source: Optical and Quantum Electronics
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7213308142