Based on the transmission characteristic of surface plasmon polaritons (SPPs), a compact plasmonic system based on a sub-wavelength metal-insulator-metal (MIM) waveguide coupled with P-shaped cavity is proposed. The results show that double Fano resonance peaks are generated in the transmission spectra, which has been studied by the finite-element method (FEM). The transmission spectrum of the system is theoretically verified by the multimode interference coupled mode theory (MICMT) perfectly. In addition, the simulation results show that the position of the resonance peaks can be adjusted by changing the structural parameters. The sensing characteristics of the resonant cavity are also studied, and the refractive index sensitivity and the figure of merit (FOM) are 2100 nm /RIU and 189.97. The results effectively improve the sensitivity and FOM of nano-scale plasmonic sensors and provide significant guidance for the application of tunable multiple Fano resonance in refractive index sensors, biosensors, optical switches and other plasmonic devices.

基于表面等离子体激元（SPPs）的传输特性，提出了一种基于亚波长金属-绝缘体-金属（MIM）波导与P型腔耦合的紧凑型等离子体系统。结果表明，在透射光谱中产生了双 Fano 共振峰，这已通过有限元方法 (FEM) 进行了研究。多模干扰耦合模式理论（MICMT）对系统的传输频谱进行了理论验证。此外，仿真结果表明，可以通过改变结构参数来调整共振峰的位置。还研究了谐振腔的传感特性，折射率灵敏度和品质因数（FOM）分别为2100 nm /RIU和189.97。