Wang Shuang, Huang Hai, Li Quan, Wang Chen, Lei Han
School of Electronic Engineering, Tianjin University of Technology and Education, Tianjin, 300222, China.
Heliyon. 2024 Oct 4;10(20):e38963. doi: 10.1016/j.heliyon.2024.e38963. eCollection 2024 Oct 30.
We theoretically and experimentally carried out an inspired type of toroidal dipole (TD) metasurfaces, which composed of a metamolecule of symmetric aluminium semicircles with a bar in the middle fabricated on polyimide substrate in the terahertz (THz) regime. It was found that the three resonances show red-shift tendency due to the increase of inductance and capacitance with the increase of semicircle's outer radius. Meanwhile, both the TD resonances and the current flowing in the metallic bar can generate the head-to-tail magnetic field distribution, which is the most prominent feature of TD phenomenon. The generation of this phenomenon is discussed deeply via the power of the multipoles, which are calculated according to the volume current density distribution data extracted from the simulations. The low frequencies (∼0.5 THz) head-to-tail magnetic field distribution is mainly attributed to TD resonance generated via the mutual effect between the two semicircles, while the same phenomenon at high frequencies (∼0.8 THz) is mainly attributed to the current flowing the middle metallic bar. The enhancement of head-to-tail magnetic field distribution leads to the increase of quality (Q) factor, and the Q factor of fabricated sample is as high as 24.5. Moreover, the electromagnetic properties in TD metasurfaces could be adjusted by the metal bar's width. The optimization of TD resonances provides opportunity to design the high Q-factor metasurfaces, and it opens up potential applications in terahertz high sensitivity devices.
我们在理论和实验上开展了一种受启发的环形偶极子（TD）超表面，它由对称铝半圆与中间有一根棒的超分子组成，该超分子制备在太赫兹（THz）波段的聚酰亚胺衬底上。研究发现，由于随着半圆外半径的增加电感和电容增大，三个共振呈现红移趋势。同时，TD共振和在金属棒中流动的电流都能产生头到尾的磁场分布，这是TD现象最显著的特征。通过多极子的功率深入讨论了这种现象的产生，多极子功率是根据从模拟中提取的体电流密度分布数据计算得出的。低频（0.5 THz）头到尾的磁场分布主要归因于两个半圆之间的相互作用产生的TD共振，而高频（0.8 THz）的相同现象主要归因于中间金属棒中流动的电流。头到尾磁场分布的增强导致品质（Q）因数增加，制备样品的Q因数高达24.5。此外，TD超表面的电磁特性可通过金属棒的宽度进行调节。TD共振的优化为设计高Q因数超表面提供了机会，并为太赫兹高灵敏度器件开辟了潜在应用。
