Study On Plasmon Properties Based On Fano Resonance

The rapid development of information technology has made the speed,miniaturization and high concentration of photonic devices become the development trend of optical communication devices.Surface plasmon(SPP)is a surface electromagnetic wave located at the metal-medium interface.They can break through the classical diffraction limits and manipulate light at the nanoscale.This makes photonic device integration and miniaturization possible,and has become the focus of many researchers.In this paper,the finite-difference time-domain method is used to study the plasmon induced absorption mechanism,Fano resonance mechanism and its application in photonic devices.The main contents include the following aspects:Based on the subwavelength scale metal-insulator-metal(MIM)waveguide,an end-coupled composite slot cavity resonator is proposed.Plasmon-induced absorption(PIA)effects are realized in a composite slot cavity resonator system compared to a perfect square cavity used as a Fabry-Perot cavity.By adding a vertical slot cavity over the perfect square slot cavity,a single or double absorption window with excellent performance can be achieved at the position of the intrinsic second-order mode transmission peak.It is also possible to simultaneously achieve the plasmon-induced absorption effect based on the inherent transmission peaks of the first-order mode and the second-order mode by embedding an annular groove in the intact cavity.According to the analysis of the phase response,anomalous dispersion occurs in the window,and the maximum delay time can be observed to be-0.18 ps.The work studied provides a unique way to stimulate and modulate the plasmon-induced absorption response,developing nanoscale integrated circuits for optical switches.We introduce a remarkably simple coplanar nanostructure consisting of two longer and one shorter graphene nanorods to support a Fano resonance,which arises from the coupling between bright mode and dark mode by breaking the geometric al symmetry.Simulation results show that the resonant frequency of the bright mode in the transmission spectrum independently adjusted via changing the lateral offset of the shorter graphene nanorod,while changing its longitudinal offset can independently adjust the resonant frequency of the dark mode.Furthermore,Fano resonance spectrum can also be regulated actively by altering the Fermi energy of graphene as well as refractive index of the surrounding media.This work proposes a unique modulation strategy of Fano resonance in metamaterials,assisting in developing potential in applications of sensor devices and some other plasmonic functional devices.