Research On All-optical Control Of Surface Plasmon Polaritons Based On Focused New Vector Light

Surface Plasmon Polaritons(SPPs)are electromagnetic oscillations formed by the interaction between free electrons and photons that are bound to the interface between a metal and a dielectric medium.SPPs can overcome the diffraction limit of optics and have properties such as extreme sensitivity to the dielectric environment,highly localized and enhanced electric fields.As a result,SPPs have been widely applied in many research fields,such as physics,chemistry,biology,and materials.To achieve the advantages of SPPs,it is crucial to excite and control their optical field.Traditional methods for exciting and controlling SPPs mostly rely on the formation of specially shaped nanoparticles or micro/nanostructures.However,these traditional methods have disadvantages such as complexity,inflexibility,and difficulty in reconstruction,which greatly limit the translation of SPPs from fundamental research to engineering applications.Therefore,it is imperative to explore new methods for exciting and controlling SPPs that are dynamic,reproducible,and free from structural limitations.In recent years,vector beams and vector vortex beams have attracted increasing attention due to their unique focusing properties.Their different polarization configurations introduce new degrees of freedom for exciting and dynamically controlling SPPs,greatly expanding the application fields of SPPs.In this paper,we mainly use high-order cylindrical vector vortex beams based on micro-focusing on smooth metal surfaces to dynamically control SPPs.The use of a high numerical aperture objective lens can provide a larger convergence angle to satisfy the wavevector matching condition of SPPs,while the different polarization and phase distributions of vector vortex beams introduce new degrees of freedom for dynamically controlling SPPs.This approach only requires adjusting the polarization and phase distribution of the incident light field to easily achieve dynamic excitation and propagation control of SPPs,without the need to construct special metal micro/nanostructures.This paper investigates in-depth the dynamic all-optical control of SPPs based on high-order cylindrical vector beams and vector vortex beams under the strong focusing model,as well as the optical chirality density enhancement based on SPPs,with the following specific content:Based on the Richards-Wolf vector diffraction theory,we first derive and establish an analytical model for the local linearly polarized vector beam and the vortex beam to excite and produce SPPs on the metal surface,including the optical field,magnetic field,energy flow,and chiral distribution,under the strong focusing model.We then study and analyze the new effects of exciting and producing SPPs under the incidence of high-order cylindrical vector beams and vector vortex beams.We discuss in detail how the polarization initial phase,angular index factor,and phase topological charge of these beams affect the distribution of SPPs optical field generated under strong focusing and how to dynamically control them.Based on surface plasmon polaritons,we construct a magnetic plasmon crystal structure composed of noble metals and magnetic transparent dielectrics and study its optical chirality density.We delve into the factors that affect the optical chirality density of micro/nanostructures and explore the physical mechanisms for enhancing their optical chirality density.This study provides new research ideas and methods for a deeper understanding of the enhancement of optical chirality density based on surface plasmon resonance.