Investigation Of The Graphene-based Plasmonic Molecules

Similar to electronic atom and molecule systems,plasmonic molecules(PMs)are composed of the interacting nanostructures where the specific collective electromagnetic behaviors are demonstrated.These behaviors include Fano resonance,slow light and electromagnetic induced transparency and etc,resulted from the coupling between the plasmons and the external disturbance.PMs have found significant applications in broad areas including fundamental sciences,information process and biochemics due to the excellent properties of high quality(Q)factors,flexible structure design,and high sensitivity to the variation of the environments.The conventional PMs are mainly noble metals such as gold and silver,which possess fixed plasmonic properties when their structures are sure.Besides,are of great loss,therefore,the metal-based SPPs properties are constrained due to the great loss of SPPs propagating on the metal surface.Graphene is 2D material composed of single layer of carbon atom,which is paid considerable attention due to its unique band structure and exceptional properties in photonics.In this paper,graphene is used to construct PMs.The properties of eigen-field and far-field extinction spectrum are systematically investigated by finite element method(FEM).The detailed research contents are as follows:First,the PMs with two graphene nanodisks are computed,and the relationships of the mode properties of TM2,1 versus the distance of disks g,modes number and chemical potential of graphene are analyzed.The research results reveal that with the changing of g,the frequency difference of the bonding and antibonding states decreases.With the increasing of mode number,the resonant frequency shifts to shorter wavelength.With the changing of graphene chemical potential,the frequency shows the anti-crossing property.Furthermore,the modes of different distance symmetrying with x and y axis versus the graphene chemical potential is studied.The results reveal manifest that with the increasing of g,the platform effect of the resonant frequency is more obvious when chemical potential is 0.4eV,and the peaksof Q-factor show a red shift.Then,by using numerical method,the graphene-based three nanodisks PMs are analyzed.The characteristic of TM1,1 versus the changing of vertex angle and scattering properties are analyzed.Because of the tunability of the graphene,the modes properties and scattering properties of PMs with chemical potential of 0.5 and0.6eV are computed.The results reveal that with the increasing of vortex angle,the symmetry of the PMs is destroyed,and the degenerate modes begin splitting and the resonant energy of the adjacent two modes shows a different change rule.The scattering properties of the PMs are obtained by the plasmonic energy spectrum.At last,the modes properties and scattering properties of the PMs versus the radius of nanodisks and graphene chemical potential are analyzed by modifying the way of symmetry of the three nanodisks.The results reveal that with the varying of the nanodisks' radius and graphene chemical potential,the symmetry of the PMs is destroyed,the degenerate modes begin splitting,the plasmonic energy increases with the reduction of radius or the increasing of chemical potential,the change rules of the Q-factor and plasmonic energy are the same.In the same way as changing vortex angle,the scattering properties of PMs can be obtained from the plasmonic energy spectrum.