Characteristics Research And Design Of Surface Plasmon Optical Waveguide Filter

Surface plasmon polaritons(SPPs)are a form of electromagnetic waves with an electromagnetic filed localized to the metal surface,which propagate along the metal surface and decay exponentially in a direction perpendicular to the metal surface.SPPs can break the traditional optical diffraction limit and have strong local electromagnetic field enhancement characteristics,its unique properties open a new development path for optical filters.Metal-Insulator-Metal(MIM)waveguide is a typical SPPs waveguide,which has the ability to manipulate light at the sub-wavelength scale,and provides an effective way to realize micro-nano photonic devices.The Plasmon-induced Transparency(PIT)effect produces a transparent window with sharp dispersion characteristics,which has huge application potential in photonic devices.In this paper,the structure of MIM waveguide filters based on SPPs is designed,and the PIT optical effect is introduced into the structure.The structure of MIM waveguide band stop and band pass filters with excellent characteristics is constructed,and the structure is gradually improved and expanded.The paper mainly includes the following aspects:Firstly,starting from the basic theoretical knowledge of SPPs,learn the basic properties and theoretical research methods of SPPs.A new dual-frequency narrowband band-stop filter based on MIM curved waveguide coupled with embedded silver bar is designed.The optical transmission characteristics of the structure are explained in detail,the mechanism of its dual-mode resonance is analyzed,and the influence of structure parameters on the filter characteristics is analyzed.Secondly,by introducing the good characteristics of the PIT optical effect into the MIM waveguide structure,a semi-closed T-waveguide side-coupled disc cavity structure band-pass filter is proposed.The PIT optical effect based on the light-dark coupling physical mechanism is realized in the branch cavity resonator and the disk cavity resonator in the system,and the narrowband bandpass filtering function is obtained.Then,by adding a gain medium in the disc cavity to compensate the intrinsic loss in the cavity,the compression filtering bandwidth is achieved and the transmission efficiency of the structure is effectively improved.Finally,the double PIT effect was achieved by adding a resonant cavity on the right side of the structure.The resonance wavelength can be adjusted by changing the radius of the resonan cavity the disc and the length of branch and the refractive index of the structure medium.Finally,based on the principle of detuning to achieve the PIT effect,a narrow-band band-pass filter with an asymmetric cross-shaped MIM waveguide structure with closed ends is proposed.Based on this,a MIM waveguide structure with an asymmetric cross-shaped waveguide side coupling disc cavity closed at both ends is proposed.Based on the detuning and light-dark coupling physical mechanism,the dual PIT effect is realized,and the dual-band pass filtering function is further obtained..Due to different physical mechanisms,the two PIT peaks can be adjusted by changing the length of the two branches and the radius of the disc cavity or the refractive index of the dielectric material filled in the disc cavity,thereby effectively selecting the filtering wavelength.