Research On Classical Wave Transmission Control Based On Artificial Microstructure

Artificial microstructure arrays,also known as artificial electromagnetic media or metamaterials,are usually in the form of periodic arrays of structural units,and are artificial periodic materials with a sub-wavelength scale.Artificial microstructure arrays have electromagnetic properties that are not found in general materials in nature,such as negative permittivity,negative permeability,and negative refractive index.Therefore,negative refraction,inverse Doppler effect and inverse tangent can be generated in artificial electromagnetic media.The microstructure units in the artificial microstructure array can be equivalent to atoms or molecules in natural materials,and the electromagnetic properties of the artificial microstructure array can be flexibly controlled by changing the unit structure and arrangement period.In recent years,metamaterials and metasurfaces with 3D and 2D artificial microstructures,respectively,have been proposed to realize miniaturized and integrated wavefield manipulation devices.Furthermore,by carefully designing geometric parameters and the arrangement of artificial microstructures,they can exhibit new properties beyond natural materials and enable new applications.Based on artificial microstructure materials,this paper designs a variety of different physical devices in the field of classical waves such as light waves and acoustic waves,and realizes the directional scattering control of light waves,metasurface magnetic mirrors,multi-band omnidirectional ventilation sound barriers,and broadband isolation.The acoustic metacage of sound has important physical significance for the design of novel optical/acoustic field control devices.The specific research content of the article is as follows:The first,a concept of a rough surface magnetic mirror is proposed,and the interface is designed by an array of artificial surface plasmon structures.This artificial surface plasmon structure supports strong magnetic dipole resonance modes by periodically inserting helical metal strips into a dielectric disk configuration.In particular,for helical structures with different outer radii,the helicity of each structure can be tuned to support the magnetic dipole modes of the same resonance frequency.To this end,a rough magnetic mirror composed of artificial surface plasmon structures of different sizes is designed,and its efficiency is calculated and compared with the smooth magnetic mirror.The rough magnetic mirror proposed in this paper can be used to enhance the interaction between light and matter with complex structures,and may also be applied to biosensing and imaging in the microwave and terahertz bands.Second,we show that the spoof plasmonic structure is able to achieve the switching of directional scattering direction at subwavelength scales by inserting a perfect electric conductor(PEC)cylinder in the hollow of the spoof plasmonic structure.Based on modal analysis,it is found that the electromagnetic responses of the core-shell structure not only be well excited,but also exhibits directional scattering by interference between the electric and magnetic dipolar resonances.We also discuss the influence of PEC cylinder radius on the performance of the directional scattering.Finally,the active tunable directional scattering is realized by switching between the two states.This work provides a feasible pathway to the subwavelength manipulation of electromagnetic wave.Moreover,it offers a simple method to switch the directional scattering direction.The proposed design approach can be easily applied to digital electromagnetic wave communication and associated applications.Third,in this paper,we propose a subwavelength closed surface consisting of radial gradient grooves for achieving localized acoustic rainbow trapping.Similar to conventional rainbow trapping based on a plane structured surface,we demonstrate that rainbow trapping can also be realized by a closed surface in the deep-subwavelength scale.In particular,the trapped spatial positions on the closed surface can be freely tuned by changing the structural parameters.Based on the advantages of the multiband response and subwavelength dimension of this structure,we propose an acoustic barrier consisting of an array of closed surfaces to achieve multiband sound insulation and high ventilation simultaneously.Investigated results indicate that this kind of acoustic barrier possesses the features of subwavelength scale,and multiband and omnidirectional responses for blocking incident acoustic waves,yet has high ventilation.Finally,we discuss the influence of the channel width on the magnitude and bandwidth of the transmission loss spectrum.The experimental results agree with our theoretical prediction that the material losses can broaden the response bandwidth,and form broadband sound insulation.The acoustic barrier consisting of localized rainbow trapping structures may have many applications in infrastructure requiring air-permeability and soundproofing.Fourth,we first design a closed surface composed of subwavelength scale radial gradient grooves.Then,we theoretically and experimentally investigate an acoustic metacage consisting of a circle closed surfaces capable of achieving multiband sound insulation and high ventilation simultaneously.As a pragmatic example,we fabricate a circular metacage consisting of ten localized structures using a three-dimensional printer and experimentally demonstrate that the metacage is capable of effectively blocking the sound with high ventilation in a broadband range,regardless of whether the sound source is excited from inside or outside the metacage.Finally,we discuss the influence of the performance of the proposed metacage in the case of arbitrary geometric shapes.The proposed acoustic metacage could open up an avenue for broadband sound insulation with high ventilation and associated applications.