Baffle Induced Sensing Enhancement for Pressure and Refractive Index Based on Fano Resonance

The sensitivity of plasma devices in pressure sensing has been undergoing significant advancements. However, the quantitative relationship between the actual deformation of the structure and the resulting optical transmission characteristics has not yet been investigated in depth. In this study, we propose a novel metal–insulator-metal (MIM) waveguide structure that exhibits a distinct transmission spectrum featuring a sharp Fano line. Notably, the incorporation of a baffle into the resonator induces the formation of a double Fano resonance, which occurs irrespective of the presence of external pressure. Remarkably, the second Fano resonance (FR2), effectively enhances the refractive index sensitivity of the system from 1400 nm/RIU to 1600 nm/RIU when the baffle is integrated into the pressure-free resonator. Furthermore, the introduction of a baffle into the pressurized cavity significantly improves the pressure sensitivity of the system. Specifically, the first Fano resonance (FR1) increases the pressure sensitivity from 2.40 nm/MPa to 6.88 nm/MPa, making it a multifunctional plasma device that functions as both an optical pressure sensor and a refractive index sensor.