Research On Hybrid Metasurface Based On Epsilon-Near-Zero Material And Metallic Subwavelength Structures

Metasurface is a two-dimensional metamaterial constructed by using subwavelength metallic or dielectric structures as functional units.The use of carefully engineered unit structures of metasurface can design metasurface devices with different electromagnetic resonance responses,and thus empowers a flexible control of electromagnetic wave under a subwavelength scale.It is expected that the hybrid metasurfaces composed by introducing other novel materials and combining them with the metamaterials will further expand the design platform.Epsilon-near-zero(ENZ)materials are special materials whose real part of permittivity is close to zero.Its unique physical effects provide a novel platform to support the coupling effect of optical systems.By combining ENZ materials with metasurfaces and making full use of their resonance coupling,it is expected to develop new metasurfaces with different functions.Focusing on the research of hybrid metasurface devices that integrates ENZ material and metallic subwavelength structures,this thesis mainly includes the following two respects:(1)A hybrid metasurface consisting of an ENZ thin layer and a subwavelength metallic asymmetric double bar array is proposed.It can realize double transparent windows in the optical communication band.The indium tin oxide layer behaves as an ENZ material and can support an ENZ mode when the real permittivity crosses zero(occurring at 1.55 ?m).The research results show that these double transparent windows originate from two different coupling effects.At 1.31 ?m,the electronmagneticlly-induced-transparency effect caused by the hybrid coupling of subwavelength double bars produces the first transparent window.At 1.55 ?m,the ENZ mode is strongly coupled to the dipole resonance mode of the long bar.This coupling effect produces mode splitting and thus creates the second transparent window.This work provides a new idea for designing metasurface devices with simple structure and unique spectral characteristics.(2)A hybrid metasurface-based broadband absorber that integrates ENZ material and metallic subwavelength structures is proposed.The ENZ mode supported by the ENZ layer is effectively coupled to the plasma resonance mode of the ‘metal-insulator-metal' structure.The simulation results show that a broadband absorption of 90% over wavelength ranges of750 nm(from 2.55 ?m to 3.3 ?m)is achieved.The performance of broadband absorption is futher verified by impedance matching principle.Moreover,the design concept can be applicable across a wide spectral range by device scaling and selection of epsilon-near-zero materials.This work offers a simple and new method for designing broadband absorbers.