Study On The Differential Sensing Properties Of Surface Plasmon MDM Waveguide Base On Fano Resonance

Surface plasmons(SPs)are electromagnetic surface waves that,when propagateing along a metal surface,have the largest field strength at the metal surface and an exponential decay field perpendicular to the metal interface,which can be excited by electrons simultaneously.It can also be excited by light waves.At the interface between the medium and the metal surface,the photonic state density of the surface plasmon is relatively high,which greatly enhances the interaction between light and matter,thereby improving the light detection capability.The unique optical properties of surface plasmons have opened up a new path for the development of optical sensors,and have become a hot spot in the study of micro-nano structures in improving the performance of photonic devices.The surface-plasma metal-dielectric-metal(MDM)waveguide sensing structure designed in this paper is integrated into the Fano resonance to achieve a significant increase in sensitivity.The differential sensing concept is introduced to realize the refractive index sensing function Expansion.The main contents of the thesis include:Firstly,starting from the theoretical basis of surface plasmon,the basic properties and theoretical research methods of SPs are studied.On this basis,the resonant cavity mechanism and Fano resonance principle of MDM waveguide are expounded,and the Fano resonance structure of the MDM waveguide toothed cavity coupled disk cavity is constructed.The structure is generated by the continuous state generated by the toothed cavity and the disk cavity.The discrete states are coupled to produce a Fano resonance.The coupling characteristics and standing wave theory are used to analyze the transmission characteristics and refractive index sensing characteristics of the structure.The effects of structural parameters on Fano resonance linearity are analyzed by theory and simulation.The above research laid the foundation for the design of the MDM waveguide Fano resonant sensing structure.Secondly,the Fano resonance dual-mode structure of the single-baffle MDM waveguide-coupled disk cavity is proposed.Under the action of the near-field,the single-metal baffle is used to form a wide continuous state and the discrete state formed by the disk cavity,coupling produces a dual mode Fano resonance.The coupling mode theory is used to analyze the transmission characteristics of the structure,and the structural parameters are optimized.Finally,the sensing characteristics are analyzed by standing wave theory.The proposed structure provides a new method for the design of multi-Fano resonant structures.Finally,based on the single-bucket coupled disk cavity,a cascade structure is introduced,and the resonant structure of the single-baffle MDM waveguide coupled disk cascade multi-Fano is proposed.Due to the unique characteristics of the cascade structure,the original mode is split,and the split discrete state is coupled with the wider continuous state formed by the single baffle to form a more sharp Fano resonance peak,which is greatly increased to some extent the resolution of the sensing structure.At the same time,through the optimization of the structural parameters,the sensitivity and the quality factor are greatly improved.Finally,based on the original refractive index sensing,the method of differential sensing is used to extend the refractive index function of many Fano resonances.Through data simulation compareson,the data shows that the sensing performance index is significantly better after referring to the differential sensing method,which shows the great application potential of the multi-Fano resonance in differential sensing.