In this paper, a sub-wavelength metal-insulator-metal (MIM) waveguide structure is proposed by using a cross-shape rectangular cavity, of which wings are coupled with two rectangular cavities. Firstly, a cross-shape rectangular cavity is placed between the input and output MIM waveguides. According to the mutual interference between bright and dark modes, three Fano resonant peaks are generated. Secondly, by adding a rectangular cavity on the left wing of the cross shaped one, five asymmetric Fano resonance peaks are obtained. Thirdly, six asymmetric Fano resonance peaks are achieved after adding another cavity on the right wing. Finally, the finite-difference-time-domain (FDTD) method and multimode interference coupled-mode theory (MICMT) are used to simulate and analyze the coupled plasmonic resonant system, respectively. The highest sensitivity of 1 000nm/RIU is achieved.

本文利用十字形矩形腔提出了一种亚波长金属-绝缘体-金属（MIM）波导结构，该矩形腔的翼与两个矩形腔耦合。首先，在输入和输出MIM波导之间放置一个十字形的矩形腔。根据明暗模式之间的相互干扰，会生成三个Fano共振峰。其次，通过在十字形的左翼上增加一个矩形腔，获得五个不对称的Fano共振峰。第三，在右翼增加另一个空腔后，获得了六个不对称的Fano共振峰。最后，利用时域有限差分法（FDTD）和多模干涉耦合模理论（MICMT）分别对耦合等离子体共振系统进行了仿真和分析。