Gorlach Maxim A, Ni Xiang, Smirnova Daria A, Korobkin Dmitry, Zhirihin Dmitry, Slobozhanyuk Alexey P, Belov Pavel A, Alù Andrea, Khanikaev Alexander B
The Department of Electrical Engineering, Grove School of Engineering, City College of the City University of New York, NY, 10031, USA.
ITMO University, Saint Petersburg, 197101, Russia.
Nat Commun. 2018 Mar 2;9(1):909. doi: 10.1038/s41467-018-03330-9.
Topological phase transitions in condensed matter systems give rise to exotic states of matter such as topological insulators, superconductors, and superfluids. Photonic topological systems open a whole new realm of research and technological opportunities, exhibiting a number of important distinctions from their condensed matter counterparts. Photonic modes can leak into free space, which makes it possible to probe topological photonic phases by spectroscopic means via Fano resonances. Based on this idea, we develop a technique to retrieve the topological properties of all-dielectric metasurfaces from the measured far-field scattering characteristics. Collected angle-resolved spectra provide the momentum-dependent frequencies and lifetimes of the photonic modes that enable the retrieval of the effective Hamiltonian and extraction of the topological invariant. Our results demonstrate how the topological states of open non-Hermitian systems can be explored via far-field measurements, thus paving a way to the design of metasurfaces with unique scattering characteristics controlled via topological effects.
凝聚态物质系统中的拓扑相变会产生诸如拓扑绝缘体、超导体和超流体等奇异物质状态。光子拓扑系统开启了一个全新的研究和技术机遇领域，与它们的凝聚态物质对应物表现出许多重要区别。光子模式可以泄漏到自由空间中，这使得通过法诺共振以光谱手段探测拓扑光子相成为可能。基于这一想法，我们开发了一种从测量的远场散射特性中检索全介质超表面拓扑性质的技术。收集到的角分辨光谱提供了光子模式的动量相关频率和寿命，从而能够检索有效哈密顿量并提取拓扑不变量。我们的结果展示了如何通过远场测量来探索开放非厄米系统的拓扑态，从而为设计具有通过拓扑效应控制的独特散射特性的超表面铺平了道路。
