The Transmission Analysis And Application Research Of Surface Plasmon Waveguide With Five Layers

With the rapid development of modern science and technology, the requirement forintegrated optical devices has become higher and higher. Due to the impact of thediffraction limit, the conventional optical devices have difficulty in achieving highintegration and miniaturization. Recently, the principles and characteristics of the surfaceplasmon have been thoroughly researched, and it is shown that the diffraction limit canbeen broken by the use of high localization and enhanced transmission of surface plasmon,the optical devices can been reduced to the sub-wavelength scales to achieve its controland transmission at the nanoscale. A large number of surface plasmon waveguides havebeen proposed and studied by scientists. Among them, the metal-dielectric-metalsurface plasmon waveguide attracts a lot of attention because of its higher limitation andsimple structure. In this paper, we propose a metal-multilayer dielectric-metal surfaceplasmon waveguide structure based on the theory of electromagnetic field and surfaceplasmon. We analyze the electric field distribution and transmission characteristics of theproposed structure by the finite-difference time-domain method and explore theapplication of the structure in the sensing field.The main work is as follows:Firstly, the basic theories and properties of the surface plasmon and surface plasmonwaveguide are introduced. We derive the dispersion relation and propagation constant ofthe surface plasmon waveguide, and investigate the electromagnetic field modes andtransmission characteristics of the metal-dielectric-metal surface plasmon waveguidesstarting from the theory and numerical simulation, which provides a theoretical basis forthe following design and research of the waveguide.Secondly, We design a metal-multilayer dielectric-metal surface plasmon waveguidestructures, and analyze its transmission characteristics using FDTD method numerically.The relationship between effective refractive index and propagation length and thethickness of the multi-layer dielectric in the middle of the presented structure isinvestigated, and the effect of the angle of the metal layer on the field distribution in thewaveguide structure is analyzed. The results show that: when the light vertically goesthrough the waveguide structure, the electromagnetic field is limited to the high refractiveindex region of the multi-layer dielectric, which leads to coupled transmission of field.The transmission performance can be improved by optimizing the thickness of the middle dielectric and the angle of the metal layer. This structure can break subwavelength-scaleoptical limitation and has the potential for application in the field of sensors andoptoelectronic integration.Finally, in order to explore the application of this metal-multilayer dielectricstructure in sensing field, We present a micro ring humidity sensor based on surfaceplasmon waveguide and carry out the numerical simulation and analysis. We study theinfluence of relative humidity variation of the external environment on the transmissioncharacteristics of the waveguide structure. the results of calculation and simulationindicate that by changing the distance between the two coupling points in the U-shapedwaveguide, the sensitivity of the sensor becomes higher and the transmission performanceis stable.The proposed humidity sensor can achieve a high sensitivity and a wide range ofthe filtering and the frequency selection at the same time, providing a theoretical basis forthe manufacture of micro optical devices.