Numerical Investigation of an Au-TiO2 Micro-Grating-Metastructure D-Shaped PCF-SPR Sensor for SARS-CoV-2-Related Biomolecular Interaction Analysis.

This study numerically investigates a D-shaped photonic crystal fiber (PCF) surface plasmon resonance (SPR) sensor integrated with an Au-TiO2 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-TiO2 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.