Surface Lattice Resonance Generated With Anisotropic Noble Metallic Nanoparticle Arrays

The localized surface plasmon resonance generated with noble metallic nanostructures can be used to focus the incident field energy to the surface of the structure effectively,thereby forming a large local field enhancement and improving the interaction of light and matter on the nanoscale,it has broad application prospects in micro-nano photonic devices.For example,noble metallic nanostructures have been used to design micro-nano photonic devices such as highly sensitive biochemical sensors,nano-light sources,and optical switches.However,the local surface plasmon resonance has a large radiation loss,which will reduce the resonance quality factor and weaken the local field enhancement,which in turn affects the performance of the micro-nano photonic device based on noble metal nanostructures.The surface lattice resonance can be excited caused by the coupling of Rayleigh anomalies and local surfaceplasmons in the arrangement of the metal nanostructures into a periodic structure,it can effectively suppress the radiation loss of the metal.The surface lattice resonance has a narrow line width and a high quality factor,which can be used to overcome the above-mentioned obstcals of local surface plasmons,and greatly enhance the performance of the above applications and has been widely studied.In general light,the metal nanoparticles can only produce surface lattice resonance perpendicular to the polarization direction.It was later discovered that multiple surface lattice resonances can be produced in the arrays of larger metal particles.Recently,parallel surface lattice resonances were found to be able to excite in nanorod arrays.Therefore,how to realize the simultaneous lattice excitation of vertical and parallel surfaces will have important significance for the modulation and application of the optical response of the array structure.In this paper,we propose anisotropic nanoparticle arrays to excite multiple surface lattice resonances,in our paper,we designed and studied two different anisotropic noble metal nanostructures,namely L-shaped gold nanorods and Split Ring Resonator.Simultaneous excitation of orthogonal and parallel surface lattice resonances using features capable of simultaneously generating dipole moments in both directions.Studies have shown that orthogonal and parallel surface lattice resonances can be excited simultaneously in the array of two metal nanostructures by selecting appropriate structural parameters:(1)The optical response of individual L-shaped nanoparticles and theinfluence of different parameters on the spectral position and peak value of their local plasmon modes were investigated.By adjusting the length,width and height,the peak position and peak value of the bonding and anti-bonding resonances can be modulated.Using the bonding mode and the anti-bonding mode to simultaneously generate the optical properties of the dipole moment in the orthogonal and parallel directions,The optical response of coupling by the bonding mode and the anti-bonding mode with Rayleigh anomalies of the array structure composed of L-shaped nanoparticles are discussed,and the near field distribution at the corresponding resonant position.The results show that both the bonding and the anti-bonding resonance can achieve the coupling with the Rayleigh anomaly,and simultaneously excite the parallel and orthogonal surface lattice resonance.(2)It is shown that for the magnetic dipole resonance,the generated equivalent magnetic dipole is oriented perpendicular to the paper plane,and the scattering fields are propagating along both directions.The optical response of a single split-ring is studied and the influence of different parameters on magnetic dipole resonance and electric quadrupole resonance spectral position and peak value.On this basis,two parameters of the split-ring array are selected for calculation,and the optical response at different periods and the near-field distribution at the corresponding resonance position are calculated.The results show that the single surface lattice resonance splits into two surface lattice resonances modulated by the x and y direction cycles simultaneously.Inaddition,the electric quadrupole resonance of the split-ring can be simultaneously excited for both surface lattice resonances,which proof that the noble metallic split-ring array is a promising platform for generating of multiple surface lattice resonances.