Design And Research Of Modulated Filter Based On Surface Plasmon Polaitons

In recent years,people are gradually exploring the application potential of surface plasmon polaritons in subwavelength optics,data storage,optical waveguide coupling effects,optical microscopes and biophotonics.A large number of studies have shown that surface plasmon polaritons(Surface Plasmon Polaritons,SPPs)are produced by dielectric projecting into metal surfaces.This is a kind of electromagnetic surface waves propagating along the metal surface formed by the interaction between electromagnetic waves and free electrons on the metal surface.By changing the structure of the metal surface,the properties of surface plasmon,especially their interaction with light,can be customized,which may lead to miniaturized photonic circuits with much smaller length scales than currently realized.Because of its ability to overcome the diffraction limit in traditional optics,it is considered to have great potential applications in modern optical highly integrated optical devices.As an important optical component in modern optical communication and on-chip optical network,all-optical filter plays an important role in signal transmission and information selection,and plays a vital role in the construction of photonic optical channel in the future.In this paper,two kinds of MIM optical waveguide structures based on surface plasmon polaritons are designed by combining the transmission characteristics of surface plasmon polaritons in optical waveguides and the coupling effect between surface plasmon polaritons and resonant cavities.By changing the coupling distance between the optical waveguide structures,a modulable optical filter is obtained.The main contents of this paper are as follows:(1)A MIM double rectangular coupled array tunable filter based on plasma induced transparency is designed.compared with the ring resonator,the SPPs filter with rectangular structure is easier to fabricate.The device is composed of multiple single double rectangular coupled resonators through spatial cascade.Finite element analysis(FEM)is used to describe the relationship between the effective refractive index(MUS)of the sensed material(liquid or gas)and the minimum transmission wavelength in the transmission spectrum based on the composite rectangular cascaded band-stop SPP filter under the perfectly matched layer absorption boundary condition.It is found that the spatially cascaded composite rectangular waveguide has a wider stopband than the traditional rectangular resonant cavity waveguide structure,and the band stop band will be redshifted when the coupling distance between the composite rectangles is changed.In addition,by introducing a small rectangular break into the PIT effect and using the projection peak generated by the PIT effect to modulate the stopband width,the size of the structure is very compact and can reach a high degree of integration of hundreds of nanometers,which has a certain reference value for the foundation and application of integrated plasma modulated optical devices.(2)A kind of concentric circle filter structure based on echo wall principle is designed.a single concentric circle structure can filter out the light wave of a single band,and the transmittance of the narrowband part is 0.021 close to zero,realizing the effect of single channel narrowband filtering.then,by changing the downward translation of the inner circle structure,a narrowband filter with non-concentric circle structure is formed,which can cause the corresponding blue shift of the filter curve.By arraying this structure,the filter stopband with a certain bandwidth can be formed,and the design of the bandstop filter is realized.according to the characteristic that the filter curve can be blue shifted by non-concentric circle translation,the stopband of the filter can be modulated,and different filtering effects can be achieved by changing the dielectric constant of the air gap.