Manifestation of PT Symmetry Breaking in Polarization Space with Terahertz Metasurfaces
Manifestation of PT Symmetry Breaking in Polarization Space with Terahertz Metasurfaces
复制标题
太赫兹超表面偏振空间中PT对称性破缺的表现
DOI：
10.1103/physrevlett.113.093901
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发表时间：
2014-08-28
影响因子：
8.6
通讯作者：
Zhang, Shuang
中科院分区：
文献类型：
--
作者：
Lawrence, Mark;Xu, Ningning;Zhang, Shuang
利用光的矢量性质和人造准原子固有的各向异性，研究了具有各向异性吸收的亚表面在极化空间中的宇称时间对称性破缺，该亚表面由两个具有相同谐振频率但损耗系数不同的垂直取向的准原子组成。通过改变它们的耦合强度，我们直接观察到系统本征偏振态的相变，本征极化椭圆的长轴经历了45度的突然旋转。尽管亚表面缺乏旋转对称性，但正是在相变处，即所谓的例外点，本征模合并成一个单一的圆偏振态。在太赫兹频率下实验实现了PT对称亚表面。
By utilizing the vector nature of light as well as the inherent anisotropy of artificial meta-atoms, we investigate parity time symmetry breaking in polarization space using a metasurface with anisotropic absorption, whose building blocks consist of two orthogonally orientated meta-atoms with the same resonant frequency but different loss coefficients. By varying their coupling strength, we directly observe a phase transition in the eigenpolarization states of the system, across which the long axis of the eigenpolarization ellipses experience a sudden rotation of 45 degrees. Despite the lack of rotational symmetry of the metasurface, precisely at the phase transition, known as the exceptional point, the eigenmodes coalesce into a single circularly polarized state. The PT symmetric metasurfaces are experimentally implemented at terahertz frequencies.