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Research On Fano Resonance Based On MDM Waveguide Coupled With Resonator And Its Sensing Characteristics

Posted on:2021-03-01Degree:MasterType:Thesis
Country:ChinaCandidate:D D TangFull Text:PDF
GTID:2428330614463631Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
Surface Plasmons Polaritons(SPPs)are a kind of behavior in which free electrons at the metal-dielectric interface generate collective oscillations and transmit along the metal-dielectric interface in the form of dense-sparse waves under an external high-frequency electromagnetic field.It is bound to the surface of the metal-dielectric interface and thus has a strong limitation.It transmits along the metal surface and decays exponentially perpendicular to the transmission direction.So surface plasmons can break through the traditional diffraction limit,which is very helpful for miniaturization and integration of optical devices.Metal-dielectric-metal(MDM)waveguide structures have many advantages such as simple structure,long transmission distance,easy fabrication,and wide frequency range.The structure of the MDM waveguide coupled resonator can generate a Fano resonance line.A significant feature of the Fano resonance line is the obvious anti-symmetry,which makes it very sensitive to changes in refractive index.This article studies the Fano resonance sensing characteristics generated when MDM waveguides are coupled to different resonators.Two coupling models of MDM waveguides and resonators with metal baffles are proposed.The first model structure is the coupling of a MDM waveguide with a metal baffle and a U-shaped cavity.The Fano resonance generated by the superposition of the broad-spectrum resonance in the waveguide and the narrow-band spectral resonance in the U-shaped cavity is mutually superimposed,we use coupling mode theory to analyze the mechanism and process of Fano resonance formation.By optimizing the structural parameters to improve the sensing performance of the structure,we found that the highest figure of merit FOM of the structure is4.7382×10~4,and the corresponding sensitivity is 800 nm/RIU.We optimized the single-sided U-shaped cavity and added a symmetrical U-shaped cavity structure to the other side of the waveguide to optimize the structural parameters to obtain the maximum FOM value of5.3478×10~4,with higher resolution and corresponding sensitivity.The corresponding sensitivity is the same as that of the single-sided U-shaped cavity.The second model structure is the coupling of MDM waveguide with metal baffle and runway-type resonator.We analyzed the sensing characteristics of the structure by changing the structure parameters.First of all,we studied the coupling of a single metal baffle with a single-sided runway resonator,and optimized the structural parameters to obtain the largest figure of merit FOM value of2.087×10~5,and the corresponding sensitivity was 866.7 nm/RIU.Secondly,when the structural parameters of the upper runway cavity are kept optimal,when a runway cavity structure rotated by90 degrees is added to the other side of the waveguide,the study found that the sensing performance at this time is better than that of the single side,and its quality factor is as high as1.412678×10~6,Sensitivity under parameters is 875 nm/RIU.Finally,when we added an asymmetric and consistent runway cavity structure on the other side of the waveguide and changed the structural parameters of the lower cavity,we found that the structure produced a double Fano resonance.We continued to study the structure and found that the dual Fano resonance was formed by the coupling of the upper and lower side cavities with the MDM waveguide.We optimized the structural parameters of the lower cavity,and found that the FOM values of the two modes of Fano resonance are 2.27901×10~5and 2.24755×10~5,and the sensitivity was 850 nm/RIU and 950 nm/RIU.Compared with the unilateral runway cavity structure,its sensing performance was better.
Keywords/Search Tags:Surface Plasmons Polaritons, MDM waveguide, Fano resonance, U-shaped cavity, runway resonator, Refractive index sensor
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