Department of Physics, Hanyang University, Seoul 133-791, Korea.
School of Electrical Engineering and Computer Science, University of Ottawa, 800 King Edward Avenue, Ottawa, Ontario, Canada K1N 6N5.
Nat Commun. 2016 Jul 18;7:12201. doi: 10.1038/ncomms12201.
Recently, synthetic optical materials represented via non-Hermitian Hamiltonians have attracted significant attention because of their nonorthogonal eigensystems, enabling unidirectionality, nonreciprocity and unconventional beam dynamics. Such systems demand carefully configured complex optical potentials to create skewed vector spaces with a desired metric distortion. In this paper, we report optically generated non-Hermitian photonic lattices with versatile control of real and imaginary sub-lattices. In the proposed method, such lattices are generated by vector-field holographic interference of two elliptically polarized pump beams on azobenzene-doped polymer thin films. We experimentally observe violation of Friedel's law of diffraction, indicating the onset of complex lattice formation. We further create an exact parity-time symmetric lattice to demonstrate totally asymmetric diffraction at the spontaneous symmetry-breaking threshold, referred to as an exceptional point. On this basis, we provide the experimental demonstration of reconfigurable non-Hermitian photonic lattices in the optical domain and observe the purest exceptional point ever reported to date.
最近，通过非厄米哈密顿量表示的合成光学材料由于其非正交本征系统而引起了人们的极大关注，这使得它们能够实现单向性、非互易性和非常规的光束动力学。这些系统需要精心配置复杂的光学势来创建具有所需度量扭曲的倾斜矢量空间。在本文中，我们报告了具有多种实部和虚部子晶格控制能力的光产生非厄米光子晶格。在所提出的方法中，通过两个椭圆偏振泵浦光束在偶氮苯掺杂聚合物薄膜上的矢量场全息干涉来产生这种格子。我们实验观察到了菲涅尔衍射定律的违反，表明了复杂格子形成的开始。我们进一步创建了一个精确的宇称时间对称格子，以在自发对称破缺阈值处演示完全非对称衍射，称为异常点。在此基础上，我们在光学域中提供了可重构非厄米光子格子的实验演示，并观察到迄今为止报道的最纯的异常点。
