Research On The Structural Design And Transmission Characteristics Of MIM Waveguide Filter Based On Surface Plasmon Polaritons

In recent years,a large number of studies have shown that surface plasmon polaritons at the interface between metals and media have local enhancement capabilities.It is an electromagnetic wave that can be propagated at the nanometer scale.Metal-Insulator-Metal waveguide is a structure commonly used to transmit SPPs.The application of MIM waveguide based on surface plasmon polaritons in the field of nano-optical device manufacturing has tremendous research value.Filters are one of the most critical components in contemporary communication equipment and control systems.Therefore,it is of great significance to study filters based on SPPs.The transmission characteristics of SPPs in the MIM waveguide and the localized effect of coupling with the resonant cavity are combined.Then,three MIM waveguide filter structures based on SPPs are designed and we optimize the filtering function of the structure by changing the geometric parameters.The main research contents are summarized as follows:(1)In this paper,a new filter structure based on four rectangular cavity MIM waveguides is designed.The simulation software COMSOL Multiphysics based on the finite element method is used to simulate the filtering structure.Firstly,cascaded three rectangular resonators are designed to realize the function of wide stopband filtering,and the spectral linewidth with transmittance less than 0.01 is 485 nm.Based on this structure,the rectangular resonant cavity is placed under the waveguide,and the two resonant modes of the cascaded rectangular cavity are coupled to each other in the same system,which causes the original resonant wavelength to no longer meet the resonant conditions and thus produces an electromagnetically induced transparency-like phenomenon.By changing the structural parameters of the rectangular cavity under the waveguide,the resonance wavelength of the electromagnetically induced transparency-like can be adjusted so that the modulation of the stopband range can be achieved.In addition,there are many reports on the realization of narrow band filtering based on the electromagnetically induced transparency-like effect.Using the effect to realize the modulation of the broadband-stop plasmonic filter is a relatively novel method.(2)The second structure is a new filter structure based on MIM waveguide with two semicircular ring resonators on different sides is designed.The direct coupling effect between a single semicircular ring resonator and waveguide can realize the function of single narrow band-stop filtering.By constructing an asymmetric semicircular ring structure,the output waveguide is affected by the resonance modes of the two radiating cavities.Moreover,the electromagnetic waves between the two radiating cavities due to antiphase oscillations cause interference and cancellation of electromagnetic waves,resulting in an lectromagnetically induced transparency phenomenon.The simulation calculation results show that this structure contains two stopbands,mode 1 and mode 2.Mode 1 has a transmittance of 0.1,and its full width at half maximum(FWHM)is 20 nm.The transmittance of mode 2 is 0.1 with the FWHM of 23 nm.The pass band is relatively smooth and the highest transmittance is 0.93.By changing the structural parameters,different wavelengths can be selected.(3)According to the transmission characteristics of the half-ring cavity,a new filter structure based on the MIM waveguide with double semicircular ring cavities on the same side is designed.Through theoretical calculation,the structure can realize the mode1 and mode 2 dual band stop filter function.The center wavelengths of the band stop is986 nm and 1230 nm,respectively.By optimizing the structural parameters,the transmittance of mode 1 is 0.13 and the FWHM of the stop band is 21 nm.The transmittance of mode 2 is 0.06 and the FWHM of the stop band is 13 nm.The structure has potential application prospects in narrow band-stop filters.