Numerical Investigation of an Au‐ TiO ₂ Micro‐Grating‐Metastructure D‐Shaped PCF

ABSTRACT

This study numerically investigates a D‐shaped photonic crystal fiber (PCF) surface plasmon resonance (SPR) sensor integrated with an Au‐TiO ₂ micro‐grating metastructure for SARS‐CoV‐2‐related biomolecular interaction analysis. The grating modulates phase matching between the core‐guided and surface plasmon polariton modes, enhancing the refractive index (RI) response. The finite element method (FEM) was used to optimize the PCF air‐hole diameters and Au‐TiO ₂ grating parameters. The sensor shows a broad RI response range of 1.19–1.43, with a maximum local wavelength sensitivity (WS) of 18 500 nm/RIU, minimum full width at half maximum (FWHM) of 10 nm, and maximum figure of merit (FOM) of 240 RIU ⁻¹ . For modeled spike RBD and anti‐RBD monoclonal IgG binding, maximum WS values of 5000 and 4782 nm/RIU were obtained. These results support compact fiber‐integrated SPR platforms for label‐free monitoring of SARS‐CoV‐2‐related RI variations, while specificity and reliability require experimental validation.