Advanced Sensing Applications Utilizing a High-Performance Narrowband Metamaterial Perfect Absorber Based on ZnO Architecture

Developing a high-performance stable plasmonic sensing device, capable of simultaneously attaining high refractive index sensitivity ( $\eta _{B}$ ) and an optimal figure of merit (FoM), remains a challenging endeavor. In this study, we present an ultrasensitive plasmonic metamaterial perfect absorber (PMPA) tailored for sensing applications. The proposed PMPA structure comprises closely spaced arrays of zinc monoxide (ZnO) nanodisks, a SiO2 dielectric spacer, and a Ag film atop a substrate, resulting in a sharp spectral absorption profile and intense electric- and magnetic-field hotspots. Utilizing a comprehensive computational modeling framework based on the finite element method, we elucidate the impact of the platform geometric configuration on optical absorption and field enhancement. By precisely controlling and manipulating the light-matter interaction within the near-infrared (NIR) region, we achieve an absorbance exceeding up to 99% with an ultranarrow resonance peak width of 2.0 nm at a plasmonic resonance of 736 nm. Quantitative analysis reveals a high refractive index sensitivity (eta(B)) of 400.0 nm/RIU and an impressive FoM value of 200.0 RIU-1. With low-loss ultranarrow spectral absorption, our findings present an improved quality factor (Q-factor) up to 368.0. Through strategic adjustment of the device configuration, we obtain robust electric-field enhancement and the localization of hotspots at the plasmonic resonance frequency. Furthermore, our study "in silico" demonstrates the platform's suitability for streptavidin molecular sensing, providing a detection range over 50 nm. These findings contribute to the advancement of plasmonic sensing capabilities, paving the way for further scientific progress and inspiring innovations in this dynamic field.