Design of a plasmonic MIM filter based on ring resonator incorporating circular air holes

A new plasmonic metal-insulator-metal (MIM) band pass filter has been proposed. This paper has shown some advantages of this novel design, which includes circular air holes, and works in a longer wavelength as well as is sensitive to the size parameters of circular air holes and the resonator. The proposed structure has a multiple-mode with two resonance wavelengths; each of them has reached an acceptable transmission peak and a higher-quality factor than the previous structures. The main advantages of this plasmonic filter combined with air holes are to present a dual-mode filter with a sharp transmission in the wavelength range from 700 to 2000 nm. The size of the geometrical parameters in this structure will be adjusted in order to successfully achieve this aim. Subsequently, the characteristics of the proposed novel filter will be improved. The proposed structure has been investigated numerically utilizing the finite difference time domain (FDTD) method and the Drude model has been used for the modeling of the metal in the structure. Our device produces the maximum quality factor (Q-Factor) as well as the minimum FWHM by the values of 62.79 and 13.13, respectively. Also, the bandwidth of the structure is smaller than the previous structures. Moreover, a higher peak of transmittance $(T_{\max}$ is 70% and the longer resonance wavelength is obtained at 1754 nm. This device is a good candidate for filtering applications which is used in optical circuits.