Zhang Ruo-Yang, Zhai Yan-Wang, Lin Shi-Rong, Zhao Qing, Wen Weijia, Ge Mo-Lin
Theoretical Physics Division, Chern Institute of Mathematics, Nankai University, Tianjin, 300071, China.
Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.
Sci Rep. 2015 Sep 2;5:13673. doi: 10.1038/srep13673.
Light traveling in time-dependent media has many extraordinary properties which can be utilized to convert frequency, achieve temporal cloaking, and simulate cosmological phenomena. In this paper, we focus on time-dependent axion-type magnetoelectric (ME) media, and prove that light in these media always has two degenerate modes with opposite circular polarizations corresponding to one wave vector , and name this effect "time circular birefringence" (TCB). By interchanging the status of space and time, the pair of TCB modes can appear simultaneously via "time refraction" and "time reflection" of a linear polarized incident wave at a time interface of ME media. The superposition of the two TCB modes causes the "time Faraday effect", namely the globally unified polarization axes rotate with time. A circularly polarized Gaussian pulse traversing a time interface is also studied. If the wave-vector spectrum of a pulse mainly concentrates in the non-traveling-wave band, the pulse will be trapped with nearly fixed center while its intensity will grow rapidly. In addition, we propose an experimental scheme of using molecular fluid with external time-varying electric and magnetic fields both parallel to the direction of light to realize these phenomena in practice.
在随时间变化的介质中传播的光具有许多非凡特性，可用于频率转换、实现时间隐身以及模拟宇宙学现象。在本文中，我们聚焦于随时间变化的轴子型磁电（ME）介质，并证明在这些介质中的光总是具有对应于一个波矢的两个简并模式，其圆偏振方向相反，我们将此效应命名为“时间圆双折射”（TCB）。通过时空互换，在ME介质的时间界面处，一对TCB模式可通过线偏振入射波的“时间折射”和“时间反射”同时出现。这两个TCB模式的叠加会导致“时间法拉第效应”，即全局统一的偏振轴随时间旋转。还研究了一个圆偏振高斯脉冲穿过时间界面的情况。如果脉冲的波矢谱主要集中在非行波频段，脉冲将被捕获，其中心几乎固定，而强度将迅速增长。此外，我们提出了一个实验方案，利用分子流体并施加与光传播方向平行的外部随时间变化的电场和磁场来在实际中实现这些现象。
