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Dual-polarization two-dimensional valley photonic crystals

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Science China(Physics,Mechanics & Astronomy) 2022年第8期65卷 102-109页

作者： Xin-Tao He Jian-Wei Liu Fu-Long Shi Ke Shen Wen-Jie Chen Xiao-Dong Chen Jian-Wen Dong School of Physics State Key Laboratory of Optoelectronic Materials and TechnologiesSun Yat-sen UniversityGuangzhou510275China

The recent realization of valley physics in photonic systems has enriched the topological phases of light with protected edge modes and shown applications in designing high-performance photonic devices. However, the widely reported valley Hall effect of light in two-dimensional systems is limited to one single polarization. Here, we present dual-polarization two-dimensional valley photonic crystals by simultaneously opening two frequency accidental degenerate Dirac cones. Two band gaps with different polarizations are characterized by opposite-valley Chern numbers, which are confirmed by the opposite-phase vortex distributions of bulk modes and opposite Berry curvatures. This situation results in the polarization-dependent refraction of bulk and edge modes, which locate in opposite valleys. The polarization-independent topological valley transport is also demonstrated. Our work shows the flexible control of light in topological photonic systems with a polarization degree of freedom and has applications in polarization multiplexing photonic devices.

关键词： topological photonics valley photonic crystals polarization

Second Chern crystals with inherently non-trivial topology

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National Science Review 2023年第8期10卷 148-155页

作者： Xiao-Dong Chen Fu-Long Shi Jian-Wei Liu Ke Shen Xin-Tao He C.T. Chan Wen-Jie Chen Jian-Wen Dong School of Physics and State Key Laboratory of Optoelectronic Materials and Technologies Sun Yat-sen University Department of Physics The Hong Kong University of Science and Technology

Chern insulators have been generalized to many classical wave systems and thereby lead to many potential applications such as robust waveguides, quantum computation and high-performance lasers. However, the band structure of a material can be either topologically trivial or non-trivial, depending on how the crystal structure is designed. Here, we propose a second Chern crystal in a four-dimensional parameter space by introducing two extra synthetic translation dimensions. Since the topology of the bulk bands in the synthetic translation space is intrinsically non-trivial, our proposed four-dimensional crystal is guaranteed to be topologically non-trivial regardless of the crystal’s detailed configuration. We derive the topologically protected modes on the lower dimensional boundaries of such a crystal via dimension ***, we observe the one-dimensional gapless dislocation modes and confirm their robustness in experiments. Our findings provide novel perspectives on topologically non-trivial crystals and may inspire designs of classical wave devices.

关键词： topological photonics synthetic dimension photonic crystals dislocation mode

Type-I Weyl points induced by negative coupling in photonic crystal

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Science China(Physics,Mechanics & Astronomy) 2021年第6期64卷 66-73页

作者： ZhaoXian Su BingYi Liu LingLing Huang YongTian Wang Beijing Engineering Research Center of Mixed Reality and Advanced Display School of Oprics and PhotonicsBeijing Instirute of TechnologyBeijing 100081China

Weyl points,which are the degenerate points in three-dimensional momentum space,have been widely studied in the photonic system,and show some intriguing phenomena such as topologically protected surface states and chiral ***-I Weyl systems possess a complete bandgap,and topologically protected surface states can be excited without disturbing the bulk *** this work,we investigate the influence of the sign of coupling coefficient on the topological property of the system and find that type-I Weyl points can be realized by introducing a negative coupling between the stacking layers of the designed photonic *** propose a new strategy to construct a type-I Weyl system by stacking the hexagonal photonic *** from the topological nontrivial photonic system with a positive coefficient,the negative couplings in the photonic system are realized by adding another resonating site between stacking *** theoretically demonstrate that the effective coupling between the resonating sites in adjacent layers sign-flips through the judicious design of the nearest coupling strength and eigenfrequency of the additional *** surface states at opposite boundaries of the proposed system have opposite group velocities,which is the feature of type-I Weyl *** study provides a new method of exploring topologically protected photonic systems and developing possible topological devices.

关键词： topological photonics Weyl semimetal photonic crystal

Robust optical mode converter based on topological waveguide arrays

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Chinese Physics B 2024年第6期33卷 197-203页

作者：徐宇翔唐文剑姜力炜吴德兴王恒许冰聪陈林 Wuhan National Laboratory for Optoelectronics and School of Optical and Electronic Information Huazhong University of Science and TechnologyWuhan 430074China

Optical mode converters are essential for enhancing the capacity of optical communication systems. However, fabrication errors restrict the further improvement of conventional mode converters. To address this challenge, we have designed an on-chip TE0–TE1mode converter based on topologically protected waveguide arrays. The simulation results demonstrate that the converter exhibits a mode coupling efficiency of 93.5% near 1550 nm and can tolerate a relative fabrication error of 30%. Our design approach can be extended to enhance the robustness for other integrated photonic devices, beneficial for future development of optical network systems.

关键词： on-chip integrated photonic devices topological photonics mode converter robustness

High-performance chiral all-optical OR logic gate based on topological edge states of valley photonic crystal

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Chinese Physics B 2023年第7期32卷 392-398页

作者：王晓蓉费宏明林瀚武敏康丽娟张明达刘欣杨毅彪肖连团 College of Physics Taiyuan University of TechnologyTaiyuan 030024China Key Laboratory of Advanced Transducers and Intelligent Control System Ministry of EducationTaiyuan University of TechnologyTaiyuan 030024China School of Science RMIT UniversityMelbourneVictoria 3000Australia

For all-optical communication and information processing,it is necessary to develop all-optical logic gates based on photonic structures that can directly perform logic ***-optical logic gates have been demonstrated based on conventional waveguides and interferometry,as well as photonic crystal ***,any defects in those structures will introduce high scattering loss,which compromises the fidelity and contrast ratio of the information *** on the spin-valley locking effect that can achieve defect-immune unidirectional transmission of topological edge states in valley photonic crystals(VPCs),we propose a high-performance all-optical logic OR gate based on a VPC *** tuning the working bandwidth of the two input channels,we prevent interference between the two channels to achieve a stable and high-fidelity *** transmittance of both channels is higher than 0.8,and a high contrast ratio of 28.8 dB is ***,the chirality of the logic gate originated from the spin-valley locking effect allows using different circularly polarized light as inputs,representing“1”or“0”,which is highly desired in quantum *** device’s footprint is 18μm×12μm,allowing high-density on-chip *** addition,this design can be experimentally fabricated using current nanofabrication techniques and will have potential applications in optical communication,information processing,and quantum computing.

关键词： topological photonics topological edge state valley photonic crystal all-optical logic gate

Theoretical research on the transverse spin of structured optical fields inside a waveguide

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Chinese Physics B 2023年第6期32卷 277-283页

作者：王智勇汪相如李岸然张开强纪玉坤钟明玉 School of Optoelectronic Science and Engineering University of Electronic Science and Technology of ChinaChengdu 610054China Jining Keli Photoelectric Industrial Co.LTD Jining 272000China

Structured optical fields inside a waveguide possess the transverse spin, i.e., the spin angular momentum perpendicular to the direction of the waveguide. The physical origin of the transverse spin can be attributed to the presence of an effective rest mass of photons in guided waves, or equivalently, to the existence of a longitudinal field component, such that the transverse and longitudinal fields together form an elliptical polarization plane. In contrary to the traditional viewpoint, the transverse spin of photons in guided waves is also quantized, and its quantization form is related to the ellipticity of the polarization ellipse. The direction of the transverse spin depends on the propagation direction of electromagnetic waves along the waveguide, such a spin-momentum locking may have important applications in spin-dependent unidirectional optical interfaces. By means of a coupling between the transverse spin of guided waves and some physical degrees of freedom, one can develop an optical analogy of spintronics, i.e., spinoptics.

关键词： transverse spin topological photonics the spin Hall effect of light spinoptics

A scheme for realizing nonreciprocal interlayer coupling in bilayer topological systems

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Frontiers of Optoelectronics 2023年第4期16卷 71-80页

作者： Xiaoxiao Wang Ruizhe Gu Yandong Li Huixin Qi Xiaoyong Hu Xingyuan Wang Qihuang Gong State Key Laboratory for Mesoscopic Physics and Department of Physics Collaborative Innovation Center of Quantum Matter&Frontiers Science Center for Nano-OptoelectronicsBeijing Academy of Quantum Information SciencesPeking UniversityBeijing 100871China Peking University Yangtze Delta Institute of Optoelectronics Nantong 226010China Collaborative Innovation Center of Extreme Optics Shanxi UniversityTaiyuan 030006China Hefei National Laboratory Hefei 230088China College of Mathematics and Physics Beijing University of Chemical TechnologyBeijing 100029China

Nonreciprocal interlayer coupling is difcult to practically implement in bilayer non-Hermitian topological photonic *** this work,we identify a similarity transformation between the Hamiltonians of systems with nonreciprocal interlayer coupling and on-site gain/*** similarity transformation is widely applicable,and we show its application in one-and two-dimensional bilayer topological systems as *** bilayer non-Hermitian system with nonreciprocal interlayer coupling,whose topological number can be defned using the gauge-smoothed Wilson loop,is topologically equivalent to the bilayer system with on-site gain/*** also show that the topological number of bilayer non-Hermitian C6v-typed domaininduced topological interface states can be defned in the same way as in the case of the bilayer non-Hermitian Su–Schrieffer–Heeger *** results show the relations between two microscopic provenances of the non-Hermiticity and provide a universal and convenient scheme for constructing and studying nonreciprocal interlayer coupling in bilayer non-Hermitian topological *** scheme is useful for observation of non-Hermitian skin efect in three-dimensional systems.

关键词： Nonreciprocal Bilayer Interlayer coupling topological photonics

On-chip topological nanophotonic devices

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Chip 2022年第4期1卷 1-21页

作者： Cui-Cui Lu Hong-Yi Yuan Hong-Yu Zhang Wen Zhao Nian-En Zhang Yan-Ji Zheng Sayed Elshahat Yong-Chun Liu Key Laboratory of Advanced Optoelectronic Quantum Architecture and Mea-surements of Ministry of Education Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic SystemsSchool of PhysicsBeijing Institute of TechnologyBeijing 100081China State Key Laboratory of Low-Dimensional Quantum Physics Department of PhysicsFrontier Science Center for Quantum InformationTsinghua UniversityBeijing 100084China

On-chip topological nanophotonic devices,which take photons as in-formation carriers with topological protection during light propaga-tion,have great application potential in the next generation photonic *** topological photonic states enable the nanophotonic de-vices to be robust and stable,immune to scattering even with imper-fect *** development,opportunities and challenges of the on-chip topological nanophotonic devices have attracted great atten-tion of scholars,and desired to be *** this review,topologi-cal devices were introduced in the order of functionalities on an in-tegrated photonic chip,*** light source,topological light waveguiding,topological light division and selection,topological light manipulation and topological light ***,we gave out-looks for predicting and promoting the performances of on-chip topo-logical nanophotonic devices from the angles of non-Hermitian sys-tems,non-Abelian topology,metasurfaces,intelligent algorithms and multiple functional topological nanophotonic *** review provides rich knowledge about on-chip topological nanophotonic *** insights in this paper will spark inspiration and inspire new thinking for the realization of topological photonic chips.

关键词： topological photonics Nanophotonic devices Photonic chip

topologically Protected Polarization Quantum Entanglement on a Photonic Chip

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Chip 2022年第1期1卷 14-18页

作者： Yao Wang Yong-Heng Lu Jun Gao Yi-Jun Chang Ruo-Jing Ren Zhi-Qiang Jiao Zhe-Yong Zhang Xian-Min Jin Center for Integrated Quantum Information Technologies(IQIT) School of Physics and Astronomy and State Key Laboratory of Advanced Optical Com-munication Systems and NetworksShanghai Jiao Tong UniversityShanghai 200240China CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics University of Science and Technol-ogy of ChinaHefeiAnhui 230026China

Quantum entanglement,as the strictly non-classical phenomenon,is the kernel of quantum computing and quantum simulation,and has been widely applied ranging from fundamental tests of quantum physics to quantum information ***,the topolog-ical phase is found inherently capable of protecting physical fields from unavoidable fabrication-induced disorder,which inspires the po-tential application of topological protection to quantum ***,we present the experimental demonstration of topologically protected quantum entangled states on a photonic *** process tomogra-phy shows that quantum entanglement can be well preserved by the topological states even when the chip material introduces disorder and relative polarization rotation in phase *** work links the fields of materials,topological science and quantum physics,opening the door to wide applications of topological enhancement in quantum regime.

关键词： Photonic chip Quantum entanglement topological photonics