Theoretical Investigation On Filter And Demultiplexer Based On Surface Plasmon Polaritons

The surface plasmon polaritons(SPPs)is a kind of waves propagating along the interface of the metal and dielectric.Due to their unique properties such as surface enhancement and high localization,they are allowed to conquer the diffraction limit and guide light waves on metal structure below the subwavelength.At present,theoretical studies on SPPs have gradually formed a significant subject and occupied an important place in the field of integrated optics.The applications based on SPPs have also made breakthroughs in a number of areas,including integrated waveguide,biosensor detection,nano-lithography,data storage and new light source,which greatly promote the performance of photonic devices and integration of optics circuits.This dissertation aimed to promote the manipulation of light waves and design of photonic devices in nanoscale.Therefore,based on the researches of SPPs on the integrated waveguide,we have proposed a novel filter and demultiplexer.The main contents of this dissertation are as follows:Firstly,based on the Drude model of metal and the Maxwell equations,we analyzed the dispersion characteristics of SPPs,and introduced the four characteristic parameters of SPPs.Besides,we described the means to stimulate SPPs on the metal surface employing the wave vector matching.Then,the principle and nature of metal-insulator-metal(MIM)waveguide were introduced.Secondly,we briefly analyzed the research models used in this dissertation.We introduced the basic principle of Finite-Different Time-Domain method(FDTD)firstly.In addition,the excitation source,the stability requirement and the boundary condition of FDTD simulation were mentioned.Next,in combination with FDTD simulation software,the coupled mode theory of the resonantors were described,and their transmission and reflection characteristics were demonstrated.Thirdly,based on the transmission characteristics of the MIM waveguide crossing,we have designed a novel filtering structure by coupling the crossing with a set of hexagonal resonators.In this structure,two MIM waveguides were orthogonal to each other to form an input port and three output channels.Coupled mode theory analysis showed that by tuning the phase between the SPP waves of different channels,the transmission efficiency in the filtered channel can reach the peak.And this process can be easily achieved by adjusting the position of the resonators.Next,the theoretical analysis was verified by FDTD simulation.In addition,the simulation showed that in this structure,the transmission efficiency and linewidth can be optimized by changing the coupling distance.Moreover,the working wavelength can be tuned by adjusting the length of resonators and the filling medium.Finally,based on the theoretical study of the filter,we have designed a novel demultiplexer.The demultiplexer was composed of a waveguide crossing and three sets of hexagonal resonators.Through reasonable layout,different wavelengths can be separated to three channels,and finally the impressive transmission efficiency and linewidth were obtained.It showed that the structure can be successfully implemented to demultiplexing in waveguide intersections.The proposed plasmonic demultiplexer may have significance for constructing complex waveguide networks and highly integrated optical communication systems.