Study On Coupling Modes Of Two-dimensional Metal Surface Resonant Cavit

Surface Plasmon Polaritons(SPPs)are electromagnetic waves generated by the collective oscillation of free electrons at metal-dielectric interface,which have strong enhancement of the local electromagnetic field and offer the possibility to operate and regulate light for optical devices.In this thesis,the coupled resonance properties of SPPs in a circular cavity are investigated by using the finite-difference time-domain method(FDTD).In this thesis,a circular cavity that can excite the SPPs WGM resonance is designed.When the metal particles are placed inside the circular cavity,the localized surface plasmon resonance(LSPR)is excited,and the excited LSPR is scattered into SPPs,the SPPs WGM splits into symmetric mode(SM)and antisymmetric mode(ASM).SM resonance is strongly coupled with the LSPR to produce two modes,positive and negative,which are very sensitive to changes in the size and position of the metal particles.Even a nanoscale metal particle placed in a circular cavity excites the LSPR and produces mode splitting,and the LSPR-induced WGM mode splitting reduces the sensing limit.The simulation results show that the wavelength shift of SM is 11.8 nm and 10.2 nm for a 1 nm change in nanoparticle radius and position,respectively.This means that a size change of 0.09 nm and a position change of 0.1nm can be sensed with a spectral resolution of 1 nm,and the strong coupling between SPP WGM and LSPR suggests a new approach for the design of sub-nanometer resolution sensors.