Pairing Toroidal and Magnetic Dipole Resonances in Elliptic Dielectric Rod Metasurfaces for Reconfigurable Wavefront Manipulation in Reflection,Advanced Optical Materials

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Pairing Toroidal and Magnetic Dipole Resonances in Elliptic Dielectric Rod Metasurfaces for Reconfigurable Wavefront Manipulation in Reflection
Advanced Optical Materials ( IF 8.0 ) Pub Date : 2018-09-17 , DOI: 10.1002/adom.201800633
Odysseas Tsilipakos ₁ , Anna C Tasolamprou ₁ , Thomas Koschny ₂ , Maria Kafesaki _{1,

3} , Eleftherios N Economou _{1,

4} , Costas M Soukoulis _{1,

2}

Affiliation

A novel approach for reconfigurable wavefront manipulation with gradient metasurfaces based on permittivity‐modulated elliptic dielectric rods is proposed. It is shown that the required 2π phase span in the local electromagnetic response of the metasurface can be achieved by pairing the lowest magnetic dipole Mie resonance with a toroidal dipole Mie resonance, instead of using the lowest two Mie resonances corresponding to fundamental electric and magnetic dipole resonances as customarily exercised. This approach allows for the precise matching of both the resonance frequencies and quality factors. Moreover, the accurate matching is preserved if the rod permittivity is varied, allowing for constructing reconfigurable gradient metasurfaces by locally modulating the permittivity in each rod. Highly efficient tunable beam steering and beam focusing with ultrashort focal lengths are numerically demonstrated, highlighting the advantage of the low‐profile metasurfaces over bulky conventional lenses. Notably, despite using a matched pair of Mie resonances, the presence of an electric polarizability background allows to perform the wavefront shaping operations in reflection, rather than transmission. This has the advantage that any control circuitry necessary in an experimental realization can be accommodated behind the metasurface without affecting the electromagnetic response.

中文翻译：

椭圆介电棒超表面中的环形和磁偶极子共振配对，用于反射中的可重构波前操纵

提出了一种基于介电常数调制椭圆介电棒的梯度超表面可重构波前操纵的新方法。结果表明，通过将最低磁偶极子米氏共振与环形偶极子米氏共振配对，而不是使用与基本电偶极子和磁偶极子相对应的最低两个米氏共振，可以实现超表面局部电磁响应所需的2π相位跨度。按照惯例进行共振。这种方法可以实现谐振频率和品质因数的精确匹配。此外，如果棒的介电常数发生变化，则可以保持精确的匹配，从而允许通过局部调制每个棒中的介电常数来构造可重构的梯度超表面。通过数值演示了超短焦距的高效可调谐光束控制和光束聚焦，凸显了薄型超表面相对于笨重的传统透镜的优势。值得注意的是，尽管使用了一对匹配的米氏共振，但电极化背景的存在允许在反射而不是透射中执行波前整形操作。这样做的优点是，实验实现中所需的任何控制电路都可以容纳在超表面后面，而不影响电磁响应。

更新日期：2018-09-17

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