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Photonic crystals and topological photonics

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Frontiers of Optoelectronics 2020年第1期13卷 2-3页

作者： c.t.chan Department of Physics The Hong Kong University of Science and TechnologyHong KongChina

the idea of photonic crystals and photonic band gap was first introduced by both Yablonovitch[1]and John in 1987[2].Photonic crystals are man-made periodic optical media in which the dispersion of light is strongly modified due to the scattering of periodically arranged dielectric or metal inclusions in the unit cell.Photonic band gaps,a frequency range in which light cannot propagate,can form as a consequence of Bragg scattering or the resonance of the inclusions in the unit cell.the existence of band gaps means that photonic crystals can serve as low-loss distributed feedback mirrors and as such,they can confine light and can be used to realize high fidelity resonant cavities that can facilitate the observation of quantum electronics phenomena.the application of such ideas to realize strong coupling between photon and exciton is achieved using planar dielectric Si periodic structures[3].When combined with a gain material,photonic crystals are obviously good platforms to realize lasing and indeed photonic crystal based lasers have attracted great interest in past three decades.the technical challenges and progress in distributed feedback organic lasers based on photonic crystals are discussed and reviewed by Fu and Zhai[4].For practical applications,nonlinear photonic crystals with different superlattices has been successfully used in quasi-phase matching and nonlinear diffraction harmonic generation.this is reviewed by Li and Ma[5].

关键词： scattering dielectric lasing

Dirac-like cone-based electromagnetic zero-index metamaterials

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Light(Science & Applications) 2021年第11期10卷 2048-2066页

作者： Yang Li c.t.chan Eric Mazur State Key Laboratory of Precision Measurement technology and Instrument Department of Precision InstrumentTsinghua UniversityBeijingChina Department of Physics Hong Kong University of Science and TechnologyKowloonHong KongChina John A.Paulson School of Engineering and Applied Sciences Harvard UniversityCambridgeMAUSA

Metamaterials with a Dirac-like cone dispersion at the center of the Brillouin zone behave like an isotropic and impedance-matched zero refractive index material at the Dirac-point frequency.Such metamaterials can be realized in the form of either bulk metamaterials with efficient coupling to free-space light or on-chip metamaterials that are efficiently coupled to integrated photonic circuits.these materials enable the interactions of a spatially uniform electromagnetic mode with matter over a large area in arbitrary shapes.this unique optical property paves the way for many applications,including arbitrarily shaped high-transmission waveguides,nonlinear enhancement,and phase mismatch-free nonlinear signal generation,and collective emission of many emitters.this review summarizes the Dirac-like cone-based zero-index metamaterials’fundamental physics,design,experimental realizations,and potential applications.

关键词： index collective realization

Hidden-symmetry-enforced nexus points of nodal lines in layer-stacked dielectric photonic crystals

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Light(Science & Applications) 2020年第1期9卷 315-324页

作者： Zhongfei Xiong Ruo-Yang Zhang Rui Yu c.t.chan Yuntian chen School of Optical and Electronic Information Huazhong University of Science and TechnologyWuhan 430074China Department of Physics The Hong Kong University of Science and TechnologyClear Water BayHong KongChina School of Physics and technology Wuhan UniversityWuhan 430072China Wuhan National Laboratory of Optoelectronics Huazhong University of Science and TechnologyWuhan 430074China

It was recently demonstrated that the connectivities of bands emerging from zero frequency in dielectric photonic crystals are distinct from their electronic counterparts with the same space groups.We discover that in an AB-layerstacked photonic crystal composed of anisotropic dielectrics,the unique photonic band connectivity leads to a new kind of symmetry-enforced triply degenerate points at the nexuses of two nodal rings and a Kramers-like nodal line.the emergence and intersection of the line nodes are guaranteed by a generalized 1/4-period screw rotation symmetry of Maxwell’s equations.the bands with a constant kz and iso-frequency surfaces near a nexus point both disperse as a spin-1 Dirac-like cone,giving rise to exotic transport features of light at the nexus point.We show that spin-1 conical diffraction occurs at the nexus point,which can be used to manipulate the charges of optical vortices.Our work reveals that Maxwell’s equations can have hidden symmetries induced by the fractional periodicity of the material tensor components and hence paves the way to finding novel topological nodal structures unique to photonic systems.

关键词： symmetry nodal dielectric

On-chip single-photon chirality encircling exceptional points

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chip 2023年第4期2卷 71-77页

作者： Zhen-Nan tian Feng Yu Xu-Lin Zhang Kai Ming Lau Li-cheng Wang Jensen Li c.t.chan Qi-Dai chen State Key Laboratory of Integrated Optoelectronics College of Electronic Sci-ence and EngineeringJilin UniversityChangchun 130012China Department of Physics The Hong Kong University of Science and TechnologyClear Water BayHong Kong 999077China

Exceptional points(EPs),which are typically defined as the degener-acy points of a non-Hermitian Hamiltonian,have been investigated in various physical systems such as photonic systems.In particular,the intriguing topological structures around EPs have given rise to novel strategies for manipulating photons and the underlying mechanism is especially useful for on-chip photonic applications.Although some on-chip experiments with the adoption of lasers have been reported,EP-based photonic chips working in the quantum regime largely re-main elusive.In the current work,a single-photon experiment was proposed to dynamically encircle an EP in on-chip photonic waveg-uides possessing passive anti-parity-time symmetry.Photon coinci-dences measurement reveals a chiral feature of transporting single photons,which can act as a building block for on-chip quantum de-vices that require asymmetric transmissions.the findings in the cur-rent work pave the way for on-chip experimental study on the physics of EPs as well as inspiring applications for on-chip non-Hermitian quantum devices.

关键词： Non-Hermitian photonics Photonic chip Exceptional points Single photons

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 reduction.Remarkably, 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

Global collaboration of eye research--personal experience

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International Journal of Ophthalmology(English edition) 2024年第6期17卷 985-990页

作者： chi-chao chan Laboratory of Immunology National Eye InstituteNational Institutes of HealthBethesdaMD 20892-1858USA Zhongshan Ophthalmic center Sun Yat-sen UniversityGuangzhou 5410060Guangdong ProvinceChina

On December 9,2023,I was privileged to be honored and participate in the Dr.chi chao chan Symposium on Global collaboration of Eye Research as the Global Eye Genetic consortium(GEGc)session,which was held in the 16th congress of the Asia-Pacific Vitreo-Retina Society(APVRS)in Hong Kong.Along with my talk on“Global collaboration of eye research:personal experience”,other prominent international speakers provided their own perspectives on opportunities for networking,collaboration,and exchange of ideas with global leaders and experts in ophthalmic practice,research,and education.

关键词： speakers collaboration Global

Key technologies and Prospects for Electric Vehicles Within Emerging Power Systems: Insights from Five Aspects

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cSEE Journal of Power and Energy Systems 2024年第2期10卷 439-447页

作者： Yalun Li Minggao Ouyang c.c.chan Xueliang Sun Yonghua Song Wei cai Yilin Xie Yuqiong Mao Department of Electrical Engineering and School of Vehicle and MobilityTsinghua UniversityBeijing 100084China School of Vehicle and Mobility Tsinghua UniversityBeijing 100084China Department of Electrical and Electronic Engineering The University of Hong KongHong Kong 999077China Department of Mechanical and Materials Engineering University of Western OntarioLondonON N6A 3K7Canada State Key Laboratory of Internet of things for Smart city University of MacaoTaipaMacao 999078China Department of Electrical Engineering Tsinghua UniversityBeijing 100084China School of Electrical and Electronic Engineering Harbin University of Science and TechnologyHarbin 150080China

the energy revolution requires coordination in energy consumption, supply, storage and institutional systems.Renewable energy generation technologies, along with their associated costs, are already fully equipped for large-scale promotion.However, energy storage remains a bottleneck, and solutions areneeded through the use of electric vehicles, which traditionallyplay the role of energy consumption in power systems. toclarify the key technologies and institutions that support EVsas terminals for energy use, storage, and feedback, the cSEEJPES forum assembled renowned experts and scholars in relevantfields to deliver keynote reports and engage in discussions ontopics such as vehicle–grid integration technology, advancedsolid-state battery technology, high-performance electric motortechnology, and institutional innovation in the industry chain.these experts also provided prospects for energy storage andutilization technologies capable of decarbonizing new powersystems.

关键词： Electric vehicles engineering philosophy highpower density motor new power system solid state batteries vehicle grid integration.

Editorial for Multiscale&Multifield coupling in Geomechanics

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第6期16卷 1919-1921页

作者： Min Wang Pengzhi Pan Andrew H.c.chan Y.t.Feng t-3 Fluid Dynamics and Solid Mechanics Theoretical DivisionLos Alamos National LaboratoryNew MexicoUSA Institute of Rock and Soil Mechanics Chinese Academy of SciencesWuhanChina School of Engineering University of TasmaniaTasmaniaAustralia college of Engineering Swansea UniversityWalesUK

We are delighted to serve as guest editors for this special issue in the Journal of Rock Mechanics and Geotechnical Engineering.the purpose of this special issue is dedicated to gathering the latest research work on Multiscale&Multifield coupling in Geomechanics,where we delve into the intricate interplay of various fields and scales that govern the behavior of geomaterials.In total,30 manuscripts from USA,china,UK,Germany,canada,India and United Arab Emirates are selected to be included in this issue.

关键词： materials. gathering mechanics

construction of a High‑Performance composite Solid Electrolyte through In‑Situ Polymerization within a Self‑Supported Porous Garnet Framework

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Nano-Micro Letters 2024年第5期16卷 56-70页

作者： An‑Giang Nguyen Min‑Ho Lee Jaekook Kim chan‑Jin Park Department of Materials Science and Engineering Chonnam National University77 Yongbong‑roBuk‑guGwangju 61186South Korea

composite solid electrolytes(cSEs)have emerged as promising candidates for safe and high-energy–density solid-state lithium metal batteries(SSLMBs).However,concurrently achieving exceptional ionic conductivity and interface compatibility between the electrolyte and electrode presents a significant challenge in the development of high-performance cSEs for SSLMBs.to overcome these challenges,we present a method involving the in-situ polymerization of a monomer within a self-supported porous Li_(6.4)La_(3)Zr_(1.4)ta_(0.6)O_(12)(LLZt)to produce the cSE.the synergy of the continuous conductive LLZt network,well-organized polymer,and their interface can enhance the ionic conductivity of the cSE at room temperature.Furthermore,the in-situ polymerization process can also con-struct the integration and compatibility of the solid electrolyte–solid electrode interface.the synthesized cSE exhibited a high ionic conductivity of 1.117 mS cm^(-1),a significant lithium transference number of 0.627,and exhibited electrochemical stability up to 5.06 V vs.Li/Li+at 30℃.Moreover,the Li|cSE|LiNi_(0.8)co_(0.1)Mn_(0.1)O_(2) cell delivered a discharge capacity of 105.1 mAh g^(-1) after 400 cycles at 0.5 c and 30℃,corresponding to a capacity retention of 61%.this methodology could be extended to a variety of ceramic,polymer electrolytes,or battery systems,thereby offering a viable strategy to improve the electrochemical properties of cSEs for high-energy–density SSLMBs.

关键词： Scalable tape-casting method Self-supported porous Li_(6.4)La_(3)Zr_(1.4)ta_(0.6)O_(12) composite solid electrolyte LiF-and B-rich interphase layers