A tunable ultra-narrow band-stop filter based on metal–insulator–metal (MIM) plasmonic waveguide with square resonator is proposed and numerically investigated using Finite-Difference Time-Domain (FDTD) simulations. Different from straight waveguides with the same width, the proposed waveguide is composed of straight waveguides and ring waveguides with different widths. It is demonstrated that the proposed structure has a full width at half maximum (FWHM) of 9 nm at wavelength of 1261 nm. The influence of the structural parameters of the waveguides and square resonator on the transmission characteristics were analyzed in detail. The resonant wavelength can be tuned by changing the refractive index in the cavity or adding a square metal in the center of the cavity, where adding a square metal in the center of the cavity can make the resonant wavelength change proportionally. Combining the two schemes can achieve specific modulation of the resonance wavelength. Such waveguide filter may have potential applications in highly integrated optical circuits.

提出了一种基于具有方形谐振器的金属-绝缘体-金属（MIM）等离子体波导的可调超窄带阻滤波器，并使用有限差分时域（FDTD）模拟进行了数值研究。与相同宽度的直波导不同，所提出的波导由不同宽度的直波导和环形波导组成。结果表明，所提出的结构在波长为 1261 nm 时具有 9 nm 的半高宽（FWHM）。详细分析了波导和方形谐振器的结构参数对传输特性的影响。谐振波长可以通过改变腔体中的折射率或在腔体中心添加方形金属来调谐，其中在腔体中心添加方形金属可以使谐振波长成比例地变化。结合这两种方案可以实现谐振波长的特定调制。这种波导滤波器可能在高度集成的光电路中具有潜在的应用。