Topology‐Induced Phase Transitions in Spin‐Orbit Photonics
Topology‐Induced Phase Transitions in Spin‐Orbit Photonics
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DOI：
10.1002/lpor.202000492
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发表时间：
2021-06
影响因子：
11
通讯作者：
Xiaohui Ling;Fuxin Guan;Xiaodong Cai;Shaojie Ma;He-xiu Xu;Qiong He;Shiyi Xiao;Lei Zhou
中科院分区：
文献类型：
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作者：
Xiaohui Ling;Fuxin Guan;Xiaodong Cai;Shaojie Ma;He-xiu Xu;Qiong He;Shiyi Xiao;Lei Zhou
自旋控制的涡旋产生和自旋霍尔效应是光学中发现的两种不同的效应，近年来得到了广泛的研究。然而，虽然这两种效应的物理起源都是由于自旋轨道相互作用，但它们的内在联系仍然不清楚，这也阻碍了对它们操纵的进一步探索。在这里，在研究自旋偏振光束在尖锐界面处的散射时，揭示了涡旋产生和通过改变入射角而产生的自旋霍尔位移之间的有趣相变。在反射/折射之后，光束包含两个分量：分别获得自旋重定向Berry相位和Pancharatnam-Berry相位的正常模式和异常模式。在反常光束内部，两类波分量获得具有不同拓扑性质的潘查拉特南-贝里相位，分别产生内禀和外禀轨道角动量（OAM）。增大入射角改变了这两种贡献的相对部分，使异常光束经历从涡旋产生到自旋霍尔位移的相变。这种有趣的效果是在特意设计的超材料板上实验观察到的，与传统板相比，其效率提高了数千倍。这些发现将两个先前发现的效应统一在一个框架中，用更清晰的图片重新解释了先前的结果，并揭示了涉及内在和外在OAM之间竞争的其他物理效应。
Spin‐controlled vortex generation and spin‐Hall effect, two distinct effects discovered in optics, have been extensively studied recently. However, while physical origins of two effects are both due to spin‐orbit interactions, their inherent connections remain obscure which also hinders further explorations on the manipulations of them. Here, in studying the scattering of a spin‐polarized light beam at sharp interfaces, an intriguing phase transition between vortex generation and spin‐Hall shift trigged by varying the incidence angle is revealed. After reflection/refraction, the beam contains two components: normal and abnormal modes acquiring spin‐redirection‐Berry phases and Pancharatnam–Berry phases, respectively. Inside the abnormal beam, two classes of wave components gain Pancharatnam–Berry phases with distinct topological natures, generating intrinsic and extrinsic orbital angular momenta (OAM), respectively. Enlarging incidence angle changes the relative portions of these two contributions, making the abnormal beam undergo a phase transition from vortex generation to spin‐Hall shift. Such intriguing effect is experimentally observed at a purposely designed metamaterial slab, exhibiting efficiency enhanced by several‐thousand times compared to that at a conventional slab. These findings unify two previously discovered effects in a single framework, reinterpret previous results with clearer pictures, and shed light on understanding other physical effects involving the competition between intrinsic and extrinsic OAM.