Research On Optical Properties Of Hyperbolic Metamaterials And The Focus Effect Of Cylindrical Vector Beams

Metamaterial is a kind of artificial material with special electromagnetic properties.As one of the research hotspots,its research focus has gradually shifted from the original left-hand material to Hyperbolic metamaterials(HMMs).In addition,in recent years,during the terahertz and near-infrared region graphene materials exhibit metallic properties and have good optical response.Changing their chemical potential and applied bias voltage can adjust the optical properties of graphene,thus replacing metal with graphene.The composition of hyperbolic metamaterials can expand the applicable band of hyperbolic metamaterials,improve structural integration and make hyperbolic hypermaterials more tunable.Therefore,research on graphene-dielectric hyperbolic metamaterials(GDM HMMs)is greatly significant.The special properties of subwavelength focusing have a wide range of applications.Cylindrical Vector Beams(CVBs)have unique light field and polarization distribution,and have become the focus of research in sub-wavelength focusing.Up to now,researchers have proposed many different methods for regulating the vector beam of the column,but the existing methods have certain limitations: the traditional lens is difficult to achieve more compact focus,and the plasmon lens cannot focusing is achieved simultaneously for two orthogonal polarization states.In addition,in recent years,the work on focusing has focused on the focusing of linearly polarized light by photonic crystals and sub-wavelength gratings.The controling mechanism and effects of these artificial microstructured materials in the case of linearly polarized light and the design perspective of microstructures are utilized.Hyperbolic metamaterials for column vector beam focusing have opened up research ideas.This paper discusses and studies the optical properties of hyperbolic metamaterials firstly.The hyperbolic dispersion relation of the graphene-dielectric multilayer film structure in the near-infrared region was analyzed by the effective medium theory(EMT).The transfer matrix method(TMM)was optimized to satisfy the large tangential wave vector condition in the GDM HMMs,the transmission spectrum of GDM HMMs with different cycle numbers is analyzed by the optimized TMM.The transmission spectrum characteristics of the whole structure are affected by the total number of cycles of the structure;further analysis and interpretation using F-P cavity theory The numerical relationship and physical mechanism of the increase of the transmission peak and the decrease of the adjacent transmission peak spacing with the increase of the overall thickness of the structure are observed.The results prove that the hyperbolic dispersion relationship of GDM HMMs in the near-infrared region,the equal-frequency curve and the transmission spectrum all indicate that the transmission of electromagnetic waves in the hyperbolic metamaterial requires large tangential wave vector conditions.Finally,the focusing characteristics of the Cylindrical Vector Beams in GDM HMMs are analyzed,and a GDM HMMs lens structure capable of focusing the column vector beam is attempted.Considering the actual preparation and application,the corresponding structure is optimized,the periodic cell size is enlarged,and the number of stacking cycles of GDM HMMs is reduced.The grating can be formed on the surface of the hyperbolic metamaterial to form a wave vector matching,and the appropriate incidence is selected according to the transmission spectrum.And the emission grating constant to realize the transmission of electromagnetic waves in GDM HMMs;in order to save the cost of modeling and calculation,this paper uses the equivalent medium method to equivalent the multilayer graphene hyperbolic metamaterial to a monolithic block,and verified The rationality is as follows: Under the two-dimensional axisymmetric coordinate system,the optimized GDM HMMs structure is constructed at a specific wavelength,and the optimal focusing effect is found by changing the grating air duty ratio.The research results of this paper provide a theoretical reference and academic reference for the establishment and analysis of GDM HMMs parameter model in the near-infrared to THz band and the design of related electromagnetic wave behavior control devices.