Ultra-narrowband high-sensitivity multispectral sensor enabled by Fabry-Perot resonances for label-free detection

Abstract

We present a highly efficient optical sensor based on the excitation of Fabry-Perot (FP) in a hybrid dielectric-metal multilayer structure. The proposed configuration, comprising a thin gold film, periodic SiO₂/Al₂O₃ layers, a sensing region, and a ground metal. This configuration supports ultra-narrowband resonances and perfect absorption, enabling precise detection of minor refractive index variations. Using the transfer matrix method (TMM), the sensor exhibits a refractive index sensitivity of 1310 nm/RIU with an exceptionally high figure-of-merit (FOM_n) of 2569 RIU⁻¹ and a quality-factor (Q) of 3025, alongside an intensity-based sensitivity of 968 RIU⁻¹ and a corresponding FOM_I of 7.06 × 10⁵ RIU⁻¹. The optical response can be tuned by altering the dielectric materials, stacking order, or structural parameters. Numerical results confirm excellent agreement with FP resonance theory, validating the design’s accuracy and robustness. These features establish the proposed sensor as a robust and versatile platform for label-free detection and advanced optical biosensing applications.