Dual-Ring Based Surface Plasmon Polaritons MIM Waveguide for High-Sensitivity Air Sensor

Abstract

Metal-insulator-metal (MIM) waveguides supporting surface plasmon polaritons (SPPs) offer a promising platform for refractive index sensing in air. However, limited sensitivity remains a major constraint for practical air-sensing applications. To obtain a high-sensitivity sensor, we propose a SPPs MIM waveguide sensor incorporating a tangent dual-ring resonator integrated with gain structure and waveguide strips. The proposed structure, fabricated on a silver substrate with air as the dielectric core, is systematically investigated using finite-difference time-domain (FDTD) simulations. By optimizing the structural parameters of the sensor model, the resonator exhibits continuous shifts in resonant wavelength as the refractive index varies from 1.00 to 1.05. A maximum sensitivity of 3540 nm/RIU is achieved. The findings demonstrate the potential of the designed sensor for highly accurate air quality monitoring, supporting the development of more effective environmental conservation strategies.