Article
Optics
Bei Yan, Yuchen Peng, Aoqian Shi, Jianlan Xie, Peng Peng, Jianjun Liu
Summary: This research explores the topological edge states and topological corner states formed by domain walls between different symmetric structures and verifies the realization of these states. The results have important implications for connecting waveguides with different symmetries to construct optical communication devices.
Article
Multidisciplinary Sciences
Tobias Biesenthal, Lukas J. Maczewsky, Zhaoju Yang, Mark Kremer, Mordechai Segev, Alexander Szameit, Matthias Heinrich
Summary: Conventional wisdom suggests that the insulating bulk is crucial for defining the topological properties of topological insulators. However, our study shows that even without an insulating bulk, fractal topological insulators composed exclusively of edge sites can still support topologically protected edge states. Additionally, we find that light transport in our topological fractal system exhibits higher velocities compared to the corresponding honeycomb lattice.
Article
Physics, Multidisciplinary
Liat Nemirovsky, Moshe-Ishay Cohen, Yaakov Lumer, Eran Lustig, Mordechai Segev
Summary: Synthetic-space topological insulators are topological systems where at least one spatial dimension is replaced by a periodic arrangement of modes. These systems can enrich the physics of topological insulators by enabling higher dimensions and nonlocal coupling. This new mechanism can be realized in photonics and cold atoms, showcasing robust unidirectional propagation in the presence of defects and disorder.
PHYSICAL REVIEW LETTERS
(2021)
Article
Physics, Multidisciplinary
Haoran Xue, Ding Jia, Yong Ge, Yi-jun Guan, Qiang Wang, Shou-qi Yuan, Hong-xiang Sun, Y. D. Chong, Baile Zhang
Summary: The study reveals the helical modes induced by dislocations in three-dimensional topological insulators, and experimentally observes and numerically verifies these modes serving as robust waveguides in three-dimensional media.
PHYSICAL REVIEW LETTERS
(2021)
Article
Multidisciplinary Sciences
Eran Lustig, Lukas J. Maczewsky, Julius Beck, Tobias Biesenthal, Matthias Heinrich, Zhaoju Yang, Yonatan Plotnik, Alexander Szameit, Mordechai Segev
Summary: The article introduces a method for achieving three-dimensional topological surface states in photonics, transforming a two-dimensional photonic waveguide array into a three-dimensional topological system by introducing the concepts of screw dislocation and synthetic dimensions, demonstrating protected edge state propagation in three dimensions.
Article
Multidisciplinary Sciences
Xing-Xiang Wang, Zhiwei Guo, Juan Song, Haitao Jiang, Hong Chen, Xiao Hu
Summary: We revealed the unique electromagnetic transport properties of a topological photonic crystal, which is originated from the Dirac frequency dispersion and multicomponent spinor eigenmodes. By precisely measuring the local Poynting vectors in microstrips of honeycomb structure, we showed that a chiral wavelet induces a global electromagnetic transportation circulating in the direction counter to the source, which is intimately related to the topological band gap specified by a negative Dirac mass. This brand-new Huygens-Fresnel phenomenon can be considered as the counterpart of negative refraction of electromagnetic plane waves associated with upwardly convex dispersions of photonic crystals, and our present finding is expected to open a new window for photonic innovations.
NATURE COMMUNICATIONS
(2023)
Article
Optics
Hongwei Wang, Guojing Tang, Yu He, Zhen Wang, Xingfeng Li, Lu Sun, Yong Zhang, Luqi Yuan, Jianwen Dong, Yikai Su
Summary: In this study, the phase-shifting theory of topological edge modes based on valley photonic crystals (VPCs) is investigated, leading to the demonstration of an ultracompact thermo-optic topological switch (TOTS) with high-efficiency phase-shifting properties and sharp-turn features. The research findings are significant for the development of topological functional devices in the fields of optical communications, nanophotonics, and quantum information processing.
LIGHT-SCIENCE & APPLICATIONS
(2022)
Article
Physics, Multidisciplinary
Christian Leefmans, Avik Dutt, James Williams, Luqi Yuan, Midya Porto, Franco Nori, Shanhui Fan, Alireza Marandi
Summary: This study reveals the emergence of non-trivial topological invariants in dissipatively coupled systems, opening up new opportunities for dissipative engineering and future research in synthetic dimensions.
Article
Optics
Daniel A. Bobylev, Daria A. Smirnova, Maxim A. Gorlach
Summary: The study demonstrates that utilizing staggered bianisotropic response can achieve topological states in photonic structures, even in simple lattices. The reason behind this behavior lies in the difference in effective coupling between resonant elements with the same and opposite signs of bianisotropy. Therefore, by encoding spatially varying bianisotropy patterns in photonic structures, flexible engineering of topologically robust light localization and propagation can be achieved.
LASER & PHOTONICS REVIEWS
(2021)
Article
Multidisciplinary Sciences
Daniel Borges-Silva, Carlos H. Costa, Claudionor G. Bezerra
Summary: In recent years, topological photonic structures have become an attractive topic in nanoscience, both for basic science and technology. In this work, we propose a two-dimensional topological photonic structure made of dumbbell-shaped dielectric rods, which includes both trivial and topological photonic crystals. By introducing an angular perturbation in the dumbbell-shaped dielectric rods, the structure exhibits pseudospin interface states between the two types of crystals. Numerical results show the opening of a bandgap and the lifting of double degeneracy at the W point, despite maintaining C6 symmetry. The robustness of these pseudospin interface states against defects, disorder, and reflection is investigated and confirmed by the numerical results. Additionally, the energy flux propagating in opposite directions in the two edge modes is shown, resembling the photonic analogue of the quantum spin Hall effect.
SCIENTIFIC REPORTS
(2023)
Article
Optics
Yu-Liang Hong, Gong-Hui Tang, Ru-Wen Peng, Ren-Hao Fan, Zhong-Li Ma, Zheng Wang, Yue Jiang, Le-Di Chen, Mu Wang
Summary: This research constructs THz photonic topological insulators and experimentally demonstrates robust, topologically protected valley transport in THz photonic crystals. It also shows the emergence of valley-polarized topological edge states and their robustness against bending and defects.
Article
Optics
Jinyu Hu, Yue Wang, Jiebin Niu, Chong Wang, Tao Liu, Lina Shi, Yongliang Zhang, Yang Xia, Kai Chang
Summary: Topological protection in photonics offers new prospects for confining and guiding light waves. For the first time, dual-polarization topological edge states are experimentally demonstrated on the silicon-on-insulator platform at optical frequencies. The topological edge states are directly observed by imaging the near fields with scattering scanning near-field optical microscopy.
LASER & PHOTONICS REVIEWS
(2023)
Article
Materials Science, Multidisciplinary
Yue He, Yong-Feng Gao, Ming Yang, Zhi-Guo Yan, Yi-Han He, Xiao-Fei Qi, Zi-Rui Liu
Summary: In this paper, we investigate the influence of Wannier center on topological edge states (TESs) and topological corner states (TCSs) in second-order topological photonic crystals (TPCs) with Kagome lattice. We propose a rhomboidal hybrid structure composed of topologically trivial and non-trivial PCs, which can achieve frequency division and beam splitting simultaneously. Additionally, we construct a parallelogram box-shaped structure of topologically non-trivial PCs with Kagome lattices and find that TCSs only appear in the close regions of acute-angled corners.
Article
Optics
Meng-Cheng Jin, Yong-Feng Gao, Hao-Zhe Lin, Yi-Han He, Ming-Yang Chen
Summary: In this study, a configuration beyond the 2D SSH model is proposed for investigating topological corner states in photonic crystals. The configuration features a simple structure, direct formation of photonic band gaps, and strong robustness of corner states against defects.
Article
Nanoscience & Nanotechnology
Antonina A. Arkhipova, Sergey K. Ivanov, Sergey A. Zhuravitskii, Nikolay N. Skryabin, Ivan Dyakonov, Alexander A. Kalinkin, Sergey P. Kulik, Victor O. Kompanets, Sergey Chekalin, Yaroslav Kartashov, Victor N. Zadkov
Summary: We report the experimental observation of periodic switching of topological edge states in dimerized fs-laser written waveguide arrays. The switching can be controlled and even completely arrested by adjusting the spacing between the arrays and the input signal power. When the topological arrays come in contact with non-topological ones, either the formation of nearly stationary topological interface mode or strongly asymmetric diffraction into the non-topological array is observed depending on the initial excitation position.
Article
Physics, Multidisciplinary
Haoran Xue, Zihao Wang, Yue-Xin Huang, Zheyu Cheng, Letian Yu, Y. X. Foo, Y. X. Zhao, Shengyuan A. Yang, Baile Zhang
Summary: Symmetry plays a crucial role in modern physics, and the interaction between crystal symmetry and gauge symmetry in topological physics can lead to new phenomena and open new frontiers in the study of topological states.
PHYSICAL REVIEW LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Hao Hu, Song Han, Yihao Yang, Dongjue Liu, Haoran Xue, Gui-Geng Liu, Zheyu Cheng, Qi Jie Wang, Shuang Zhang, Baile Zhang, Yu Luo
Summary: This study extends the concept of band topology from wave systems to diffusion dynamics and experimentally observes the emergence of stable topological edge decays within the gap of bulk decays.
ADVANCED MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Xinrong Xie, Maoliang Wei, Yumeng Yang, Yuanzhen Li, Kunhao Lei, Zijian Zhang, Chi Wang, Chuyu Zhong, Lan Li, Zuojia Wang, Wei E. I. Sha, Erping Li, Haoran Xue, Zhaoju Yang, Luqi Yuan, Hongsheng Chen, Hongtao Lin, Fei Gao
Summary: Topological and non-Hermitian physics offer powerful tools for manipulating light, and recent studies on their interplay have yielded fruitful results in various photonic settings. The realization of this interplay currently focuses on enabling energy exchange between topological systems and the environment. However, it has been discovered that a non-Hermitian phenomenon called the anti-parity-time phase transition naturally emerges from a Hermitian system realized by coupled topological valley waveguides. This phase transition gives rise to two exotic topological superstates in the spectral domain and enables the realization of a photonic topological bi-functional device on a silicon-on-insulator platform at telecommunications frequencies.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Optics
Qiang Wang, Y. D. Chong
Summary: Non-Hermitian photonic lattices combine energy non-conservation with bandstructure physics, resulting in unique properties absent in conventional materials or photonic metamaterials. This tutorial introduces the key concepts in the design and implementation of non-Hermitian photonic lattices, including the features of non-Hermitian lattice Hamiltonians and their bandstructures, the role of non-Hermitian lattice symmetries, and the topological characterization of non-Hermitian bandstructures. It also surveys important non-Hermitian lattice designs and the photonics platforms for their realization, concluding with discussions on future developments in the field.
JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS
(2023)
Article
Optics
Dongjue Liu, Zihao Wang, Zheyu Cheng, Hao Hu, Qijie Wang, Haoran Xue, Baile Zhang, Yu Luo
Summary: Non-Hermiticity can have a significant impact on the topology of photonic/electronic lattices, leading to the emergence of point gaps, which have been the subject of much research interest. While the influence of point-gap topology on the bulk-boundary correspondence for line gaps has been extensively studied, a topological lattice that simultaneously undergoes transitions in line-gap and point-gap topology has not been reported. Here, we propose a strategy to manipulate line-gap and point-gap topology simultaneously in non-Hermitian lattices. By introducing asymmetric intercell coupling, we demonstrate the process of line-gap topological transition. By further considering nonreciprocal coupling between nearest neighboring unit cells, simultaneous topological transitions in point-gap and line-gap can be achieved. Finally, we discuss the influence of next nearest coupling on non-Hermitian line-gap and point-gap topology.
LASER & PHOTONICS REVIEWS
(2023)
Article
Physics, Multidisciplinary
Baile Zhang, Y. D. Chong, Qiang Wang, Changyan Zhu, Xu Zheng, Haoran Xue
Summary: In a Hermitian system, bound states have quantized energies, while free states form a continuum. However, this principle fails in non-Hermitian systems, as demonstrated by analyzing imaginary momentum and Landau-type vector potential non-Hermitian continuous Hamiltonians. The eigenstates, called continuum Landau modes (CLMs), have Gaussian spatial envelopes and occupy a continuum in the complex energy plane. Realizable 1D and 2D lattice models hosting CLMs are presented, with localized lattice eigenstates that match features of the continuous model. These lattice models can function as a rainbow trap, concentrating excitation at a position proportional to the frequency, or as a wave funnel, concentrating input excitation onto a boundary over a wide frequency bandwidth. Unlike recent funneling schemes based on the non-Hermitian skin effect, these lattice designs require simple reciprocal couplings.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Multidisciplinary
Yuanzhen Li, Su Xu, Zijian Zhang, Yumeng Yang, Xinrong Xie, Wenzheng Ye, Feng Liu, Haoran Xue, Liqiao Jing, Zuojia Wang, Qi-Dai Chen, Hong -Bo Sun, Erping Li, Hongsheng Chen, Fei Gao
Summary: Photonic topological states connected with far-field degrees of freedom have been extensively studied. The emergence of higher-order topological insulators offers new paradigms to localize or transport light in extended dimensionalities. In this study, polarization-orthogonal second-order topological corner states were observed on a designer-plasmonic kagome metasurface in the far field. The phenomenon relies on the projection of far-field polarizations to intrinsic parity degrees of freedom and the parity splitting of plasmonic corner states.
PHYSICAL REVIEW LETTERS
(2023)
Editorial Material
Physics, Multidisciplinary
Zhiwei Guo, Haoran Xue, Yang Long, Chengzhi Qin, Liang Jin
FRONTIERS IN PHYSICS
(2023)
Article
Multidisciplinary Sciences
Haoran Xue, Z. Y. Chen, Zheyu Cheng, J. X. Dai, Yang Long, Y. X. Zhao, Baile Zhang
Summary: The band topology of materials relies on topological invariants called topological charges, which describe the twisted nature of Bloch wavefunctions in momentum space. Under space-time inversion symmetry, a different characteristic class called the Stiefel-Whitney class is required for the topological classification of real Bloch wavefunctions. In this study, the authors experimentally demonstrate the presence of two Stiefel-Whitney topological charges in a three-dimensional acoustic crystal, leading to a doubled bulk-boundary correspondence.
NATURE COMMUNICATIONS
(2023)
Review
Physics, Applied
Zhi-Kang Lin, Qiang Wang, Yang Liu, Haoran Xue, Baile Zhang, Yidong Chong, Jian-Hua Jiang
Summary: There are two prominent applications of topology in the physics of materials: band topology and topological defects. Recent experimental advancements have begun to probe their interactions. Topological lattice defects in materials offer a platform to explore a diverse range of phenomena, such as robust topological-bound states, fractional charges, topological Wannier cycles, chiral and gravitational anomalies, topological lasers, and non-Hermitian skin effects.
NATURE REVIEWS PHYSICS
(2023)
Article
Materials Science, Multidisciplinary
He Gao, Haoran Xue, Zhongming Gu, Linhu Li, Weiwei Zhu, Zhongqing Su, Jie Zhu, Baile Zhang, Y. D. Chong
Summary: This study introduces a variant of the non-Hermitian skin effect, called the anomalous Floquet NHSE, achieved by fixed on-site gain or loss in a one-dimensional coupled ring resonator lattice. The experimental implementation in an acoustic lattice shows good agreement with theoretical predictions, with a broadband asymmetric transmission achieved with a relative bandwidth of around 40%.
Article
Materials Science, Multidisciplinary
Qiang Wang, Changyan Zhu, You Wang, Baile Zhang, Y. D. Chong
Summary: The non-Hermitian skin effect is a phenomenon where certain lattice Hamiltonians have a large number of eigenmodes condensed to the boundary. Coupled nonlinear resonator lattices can function as reciprocal quantum amplifiers, allowing for strong photon amplification and directional photon amplification between different lattice corners.
Article
Optics
Hau Tian Teo, Haoran Xue, Baile Zhang
Summary: We present the design of a non-Hermitian photonic Chern insulator that allows tuning of its band topology through gain and loss parameters. Numerical simulations demonstrate a topological phase transition accompanied by the closing and reopening of a Dirac cone. The results suggest the possibility of non-Hermitian control over band topology in a Chern insulator setting and potential applications in active topological photonic devices.
Article
Materials Science, Multidisciplinary
Zihao Wang, Dongjue Liu, Hau Tian Teo, Qiang Wang, Haoran Xue, Baile Zhang
Summary: This study designs and demonstrates a three-dimensional photonic crystal that achieves a higher-order Dirac semimetal phase, paving the way for exploring higher-order topological semimetal phases in three-dimensional photonic systems.