Optical refractive index sensor with two plasmonic double-square resonators for simultaneous sensing of human blood groups

Abstract

In this study, we investigated a compact refractive index (RI) sensor containing two concentric double-square resonators with plasmonic metal/insulator/metal (MIM) structures to facilitate the sensing of human blood groups. The sensing surveys were conducted using the finite difference time domain method. Intensive coupling occurred due to momentum matching between the equivalent modes of the square resonators. The results demonstrated that the modes of resonance had high contraction ratios in this device and increasing the material RI in the resonators led to remarkable red shifts of the dip wavelengths. The sensing performance was enhanced by using two multiple concentric resonators to effectively increase the strength of the light–analyte interaction, which is useful for sensing applications. Our proposed nano-sensor obtained sensitivity, sensing resolution, and figure of merit values of 1380 nm/RIU, 7.24 × 10−4 RIU, and 104 RIU‒1, respectively. The effects of the geometrical variables on the output spectra were studied in detail. Furthermore, this MIM-based sensor may have potential applications in highly integrated optical circuits for monitoring and filtering tasks.