Design And Research Of Optical Sensor Based On Mim Surface Plasma Optical Waveguide

Surface Plasmon Polaritons(SPPs)have become one of the hotspots in nanophotonics research due to their characteristics such as sub-wavelength constraint,transmission enhancement effect,and breakthrough of the diffraction limit.Its essence is a kind of dense electron wave propagating along the interface between the medium and the metal surface formed by the interaction of free electrons and incident photons on the metal surface.Optical devices based on surface plasmons provide the possibility for integration and miniaturization of photonic devices.For example,beam splitters,sensors,and filters have been successfully designed.The Fano effect associated with surface plasmon metal nanostructures is susceptible to the surrounding environment,so it has important application values in biosensing.Based on the research at home and abroad,this paper focuses on the design of three types of optical sensors based on metal-insulator-metal(MIM)optical waveguides.The corresponding transmission characteristics are studied using theoretical analysis and numerical simulation,and the function and structure parameters of the device have been optimized.The main work is divided into the following aspects:1.The development history and related applications of surface plasmons are introduced.Based on Maxwell’s equations and boundary conditions,the relevant characteristics and principles of surface plasmons are analyzed and derived.In addition,the calculation method and the basic principle of Finite-Difference Time-Domain(FDTD)are introduced in detail.2.The scattering matrix theory and time-domain coupled mode theory based on surface plasmon polaritons are explained in detail,and the simplified process of the scattering matrix theory in the tooth-shaped coupling system is stated.The multiple interferences coupled mode theory is further deduced from the coupled mode theory.Then the two theoretical models are used to curse fitting in the sensor structures theoretically,which further confirmed the rationality of the structure.3.Three types of MIM waveguide structures consisting of rectangular and tooth-shaped cavities are proposed.In order to explore the optical characteristics of these structures,FDTD method is used for numerical simulation.Simulation results show that in the transmission spectra of the first and second waveguide structures,there are three Fano resonances,and the third structure shows four Fano resonances.Because their physical mechanisms are different,the resonant wavelength of each Fano peak can be adjusted independently by changing the corresponding cavity parameters.This independent adjustability is of great significance for practical applications.Among them,the first structure is a symmetrical structure,which has the characteristics of simple manufacture and high transmittance,and the corresponding sensitivity and quality factor can be as high as 1100 nm / RIU and 91.Compared with the previous structure,the second structure uses a part of the rectangular cavity as part of the output cavity of another resonant cavity.The sensitivity and quality factor can reach 985 nm / RIU and 54.The third structure innovatively uses a composite structure as the broadband of the system whose advantage is that the physical space of the broadband is relatively wide,which is good for narrow-band coupling.Its sensitivity and quality factor can reach 1120 nm / RIU and 80.The nano-sensor structure designed in this paper has the potential to be widely used in photonic integrated circuits and chips.