摘要
本文提出一种具有宽带吸收与极化转换可切换的太赫兹超表面,通过调节二氧化钒电导率可实现太赫兹波吸收和极化转换功能灵活切换.当二氧化钒处于金属状态时,该超表面表现为宽带吸收器,在6.32-18.06 THz范围吸收率大于90％,相对带宽为96.3％.当二氧化钒为绝缘状态时,该结构在2.41-3.42 THz,4.78-7.48 THz和9.53-9.73 THz频率范围表现为极化转换器,极化转换率大于90％.该超表面结构可以用于太赫兹波探测、太赫兹通信以及太赫兹传感等领域应用.
Abstract
Metasurfaces can realize flexible modulation of electromagnetic waves at the wavelength level.However,the reported functions of metasurface are usually fixed and cannot be changed,once its structural design is completed.The designed metasurface cannot meet the requirements for flexible regulation of terahertz waves.We find that the phase change material of vanadium dioxide can achieve a transition from insulating state to metallic state through thermal,electrical,or light excitation,and the phase transition of this material is reversible.Therefore,using vanadium dioxide to form a composite metasurface can achieve dynamic modulation of terahertz waves.In this study,we propose a terahertz metasurface with switchable broadband absorption and polarization conversion.The proposed metasurface is composed of a 9-layer structure stacked from bottom to top with a combination pattern of different dielectric layers.By adjusting the conductivity of vanadium dioxide,the designed metasurface can achieve flexible switching between terahertz wave absorption function and polarization conversion function.When the vanadium dioxide is in the metal state,the designed metasurface behaves as a broadband absorber with an absorption rate of more than 90％in a range of 6.32-18.06 THz and a relative bandwidth of 96.3％.When the vanadium dioxide is in the insulated state,the designed structure acts as a polarization converter in a frequency range of 2.41-3.42 THz,4.78-7.48 THz,and 9.53-9.73 THz,respectively,with a polarization conversion rate of over 90％.We believe that this metasurface structure will have good applications in the fields of terahertz wave detection,terahertz switches,terahertz filtering,terahertz communication,and terahertz sensing.
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