Experimental observation of a polarization vortex at an optical bound state in the continuum
Experimental observation of a polarization vortex at an optical bound state in the continuum
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DOI：
10.1038/s41566-018-0177-5
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发表时间：
2018-07-01
期刊：
影响因子：
35
通讯作者：
Koenderink, A. Femius
中科院分区：
文献类型：
--
作者：
Doeleman, Hugo M.;Monticone, Francesco;Koenderink, A. Femius
连续介质中的光学束缚态（BIC）是由光子结构支持的状态，这些光子结构与自由空间辐射兼容，但对于一个特定的面内动量和波长（1，2）完全束缚。最近，有人预测，在BIC动量-频率条件附近由这种模式辐射的光应该在其远场偏振分布中显示涡旋，使BIC受到拓扑保护（3）。在这里，我们研究了一个一维的光栅支持一个横向磁模式与BIC近700 nm波长，验证BIC的存在，使用反射测量，这表明反射功能消失。使用k-空间偏振测量，我们测量了BIC周围反射的全偏振态，突出了拓扑涡旋的存在。我们使用一个电磁偶极子模型来解释所观察到的BIC通过两个辐射通道之间的破坏性干涉，弗里德里希-温特根型BIC 4的特性。我们的发现揭示了BIC的起源，并验证了它们的拓扑性质。
Optical bound states in the continuum (BICs) are states supported by a photonic structure that are compatible with free-space radiation, yet become perfectly bound for one specific in-plane momentum and wavelength(1,2). Recently, it was predicted that light radiated by such modes around the BIC momentum-frequency condition should display a vortex in its far-field polarization profile, making the BIC topologically protected(3). Here, we study a one-dimensional grating supporting a transverse magnetic mode with a BIC near 700 nm wavelength, verifying the existence of the BIC using reflection measurements, which show a vanishing reflection feature. Using k-space polarimetry, we measure the full polarization state of reflection around the BIC, highlighting the presence of a topological vortex. We use an electromagnetic dipole model to explain the observed BIC through destructive interference between two radiation channels, characteristic of a Friedrich-Wintgen- type BIC4. Our findings shed light on the origin of BICs and verify their topological nature.