Polarization Conversion Properties Of Single-layered Hollow S-type Metamaterial

Metamaterial is a kind of artificially designed subwavelength periodic structure and has many novel physical properties that are unavailable in conventional natural materials.Metamaterial polarization control components have important applications in the fields of polarization imaging,sensing measurement and wireless communication.The polarization state of electromagnetic wave can be controlled effectively by utilizing chiral and anisotropic metamaterials.Especially,the single-layered polarization control components are of great significance for the miniaturization and integration of nanophotonic systems.On the other hand,coherent control technique provides a new way to investigate tunable polarization properties,and has a distinct advantage towards optical switches and modulators for real-time control of polarization states.We carry out the related research work focusing on the polarization conversion and tunable properties of single-layered metamaterials.A hollow S-shaped single-layered metamaterial is proposed and finite element algorithm is used to systematically analyze the polarization properties and physical mechanism of the metamaterial under the incidence of single beam and coherent control light.The detailed research work is as follows:(1)We have designed a single-layered hollow S-shaped metamaterial.The results show that the cross-polarization conversion efficiency of the structure is identical for both x-polarized light and y-polarized light,while the cross-polarization rotation properties of y-polarized light is better than that of x-polarized light incidence at resonant wavelengths.Despite the efficiency of the single-layered polarization metamaterial is low,it has the advantages of simple structure and easy preparation.What’s more,we have analyzed the influence of structural parameters(the thickness of metal layer and so on)on the polarization properties of the hollow S-shaped structure in detail.(2)Based on the single-layered hollow S-type metamaterial and the optimal design of the structure,two kinds of switchable polarization control components are proposed using coherent control technology.One is dual-wavelength switchable polarization control component.Switchable polarization conversion properties can be achieved by controlling the phase difference of two coherent beams at two resonant wavelengths.The maximum cross-polarization conversion energy of the output light is 4 times that of single beam light incidence,and the modulation depths of switching effect are higher than 99%.We investigate the dependence of cross-polarization properties of output light on phase difference at resonant wavelengths.The physical mechanism of the dual-wavelength switching effect is derived from the strength regulation of the "in-phase mode" response of different phase difference incident lights.The other is a multi-wavelength tunable polarization switchable component.When the phase difference of coherent light is 0° and 180°,the resonant response properties of metamaterial are single-wavelength and dual-wavelength,respectively.The wavelength tunable polarization switching component is achieved by controlling the phase difference.The results show that the conversion between the "in-phase mode" and the "anti-phase mode" leads to the multi-wavelength tunable polarization switching properties of single-layered metamaterial.