Study On Optical Properties And Applications Of Metallic Microstructures

Surface plasmon refers to the collective oscillation of free electrons on the surface of metallic nanostructures.When electromagnetic waves are incident to metallic nanostructures,the interaction between free electrons and incident photons produces the plasmonic resonance at the metal-medium interface.Because of its excellent optical properties,such as near-field electric field enhancement and localized surface electromagnetic mode,it has shown great potential applications in enhanced nonlinear effect,super-resolution imaging,integrated optical path,biosensor and so on.This paper mainly studies and analyzes the asymmetric transmission characteristics of chiral metallic nanostructures and the enhanced second-order nonlinear response of two-dimensional materials by surface plasmon from theoretical and experimental aspects,including the following aspects:(1)Firstly,the realization conditions of asymmetric transmission are analyzed according to the transmission matrix.Then,based on the results of electromagnetic simulation,a sandwiched chiral metamaterial is proposed,which is composed of metal grating and Z-shaped hole structure.The asymmetric transmission of linear polarization wave is achieved at about 236.5 THz.The relationship between the structure parameters and the asymmetric transmission effect is analyzed.By designing the structure parameters,the diode-like effect is realized at 239 THz.At the same time,we also analyze the optical rotation of the structure,and prove that it has a strong cross polarization conversion rate.This provides a method and a way for the realization of the unidirectional electromagnetic wave transmission equipment and the polarization converter of the linear polarization wave.(2)Monolayer transition metal dichalcogenides(TMDs)possess large second-order nonlinear responses due to the broken inversion symmetry,which can extend their intriguing applications in nonlinear nanophotonics and optoelectronics.However,the atomic thickness of monolayer TMDs severely decreases the interaction length with free light with respect to bulk materials,leading to rather low second-harmonic generation(SHG)conversion efficiency.Here,we demonstrate a hybrid structure consisting of a monolayer MoS₂on a suspended perforated silver film,on which the SHG signal emitted from the monolayer MoS₂is enhanced by more than three orders of magnitude at room temperature.The pronounced SHG enhancement is attributed to the distinct electric field amplification nearby the nanoholes,which is induced by the symmetric surface plasmon polaritons(SPPs)existing in the ultrathin suspended silver grating.Our results reported here may establish the substrate-free engineering of nonlinear optical effects via plasmonic nanostructures on demand.The optical properties of the proposed metallic micro-nano structures are based on the surface plasmon resonance,which provides new ideas and methods for the application of surface plasmon.