On the origin of pure optical rotation in twisted-cross metamaterials.
On the origin of pure optical rotation in twisted-cross metamaterials.
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DOI：
10.1038/srep30307
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发表时间：
2016-07-26
影响因子：
4.6
通讯作者：
Hibbins AP
中科院分区：
文献类型：
--
作者：
Barr LE;Díaz-Rubio A;Tremain B;Carbonell J;Sánchez-Dehesa J;Hendry E;Hibbins AP
我们对扭曲交叉超材料的响应进行了实验和计算研究，该超材料在 19 GHz 至 37 GHz 的宽频带内提供近乎无色散的旋光。我们比较了两种不同的几何形状：首先，由金属十字阵列组成的双层结构，其中第二层中的十字围绕层法线扭曲；其次，第二层被替换为原始层的补充层，即十字形孔阵列。通过数值建模，我们确定了这两种结构中旋转效应的起源。在这两种情况下，纯旋光发生在两个传输最小值之间的频带中，其中发生电偶极矩和磁偶极矩的对准。在交叉/交叉超材料中，传输最小值出现在耦合交叉的对称和反对称谐振处。相比之下，在交叉/互补交叉结构中，传输最小值与交叉的偶极子和四极模式相关，其频率似乎是交叉层本身固有的。因此，发现旋光带宽相对独立于层分离。
We present an experimental and computational study of the response of twisted-cross metamaterials that provide near dispersionless optical rotation across a broad band of frequencies from 19 GHz to 37 GHz. We compare two distinct geometries: firstly, a bilayer structure comprised of arrays of metallic crosses where the crosses in the second layer are twisted about the layer normal; and secondly where the second layer is replaced by the complementary to the original, i.e. an array of cross-shaped holes. Through numerical modelling we determine the origin of rotatory effects in these two structures. In both, pure optical rotation occurs in a frequency band between two transmission minima, where alignment of electric and magnetic dipole moments occurs. In the cross/cross metamaterial, the transmission minima occur at the symmetric and antisymmetric resonances of the coupled crosses. By contrast, in the cross/complementary-cross structure the transmission minima are associated with the dipole and quadrupole modes of the cross, the frequencies of which appear intrinsic to the cross layer alone. Hence the bandwidth of optical rotation is found to be relatively independent of layer separation.