Metal-insulator-metal (MIM) waveguide has deep sub-wavelength field confinements, which makes it an important component in many aspects. In MIM structure, both of the symmetric and anti-symmetric modes could be supported. However, the anti-symmetric mode was hardly used in the SPP-based devices due to the critical excitation condition. Here, we demonstrate anti-symmetric mode excitation and Fano resonance in a compact MIM-based plasmonic structure. By changing the position of the output channel, the symmetric mode is suppressed and only anti-symmetric mode is excited. Then, we tune the position of the output channel; anti-symmetric and symmetric mode are both achieved. Furthermore, Fano resonance is realized due to the coupling between anti-symmetric mode and symmetric mode. In addition, we analyze the effects of the parameters of the structure on the transmission spectra, and a plasmonic refractive index sensor with sensitivity about 800 nm/RIU and 1100 nm/RIU based on different waveguide modes is also realized. The proposed structure provides a novel method to achieve anti-symmetric mode excitation, and it has important applications in nanophotonic devices such as filter, sensor, and photoswitch, and has important significance in achieving all-optical on-chip integration.

金属-绝缘体-金属（MIM）波导具有较深的亚波长场限制，这使其成为许多方面的重要组件。在MIM结构中，可以同时支持对称和反对称模式。然而，由于临界激励条件，几乎没有在基于SPP的设备中使用反对称模式。在这里，我们展示了一个紧凑的基于MIM的等离子体结构中的反对称模式激发和Fano共振。通过更改输出通道的位置，可以抑制对称模式，并且仅激发反对称模式。然后，我们调整输出通道的位置；反对称和对称模式都可以实现。此外，由于反对称模式和对称模式之间的耦合，实现了法诺共振。此外，我们分析了结构参数对透射光谱的影响，并实现了基于不同波导模式的灵敏度分别为800 nm / RIU和1100 nm / RIU的等离激元折射率传感器。所提出的结构提供了一种实现反对称模式激发的新颖方法，并且在诸如滤波器，传感器和光电开关的纳米光子器件中具有重要的应用，并且对于实现全光学片上集成具有重要的意义。