The paradigm shift of Hermitian systems into the non-Hermitian regime profoundly modifies inherent property of the topological systems, leading to various unprecedented effects such as the nonHermitian skin effect(NHS...The paradigm shift of Hermitian systems into the non-Hermitian regime profoundly modifies inherent property of the topological systems, leading to various unprecedented effects such as the nonHermitian skin effect(NHSE). In the past decade, the NHSE has been demonstrated in quantum, optical and acoustic systems. Beside those wave systems, the NHSE in diffusive systems has not yet been observed, despite recent abundant advances in the study of topological thermal diffusion. In this work,we design a thermal diffusion lattice based on a modified Su-Schrieffer-Heeger model and demonstrate the diffusive NHSE. In the proposed model, the asymmetric temperature field coupling inside each unit cell can be judiciously realized by appropriate configurations of structural parameters. We find that the temperature fields trend to concentrate toward the target boundary which is robust against initial excitation conditions. We thus experimentally demonstrated the NHSE in thermal diffusion and verified its robustness against various defects. Our work provides a platform for exploration of non-Hermitian physics in the diffusive systems, which has important applications in efficient heat collection, highly sensitive thermal sensing and others.展开更多
Recent breakthroughs in deep learning have ushered in an essential tool for optics and photonics,recurring in various applications of material design,system optimization,and automation control.Deep learning-enabled on...Recent breakthroughs in deep learning have ushered in an essential tool for optics and photonics,recurring in various applications of material design,system optimization,and automation control.Deep learning-enabled on-demand metasurface design has been the subject of extensive expansion,as it can alleviate the time-consuming,low-efficiency,and experience-orientated shortcomings in conventional numerical simulations and physics-based methods.However,collecting samples and training neural networks are fundamentally confined to predefined individual metamaterials and tend to fail for large problem sizes.Inspired by object-oriented C++programming,we propose a knowledge-inherited paradigm for multi-object and shape-unbound metasurface inverse design.Each inherited neural network carries knowledge from the"parent"metasurface and then is freely assembled to construct the"offspring"metasurface;such a process is as simple as building a container-type house.We benchmark the paradigm by the free design of aperiodic and periodic metasurfaces,with accuracies that reach 86.7%.Furthermore,we present an intelligent origami metasurface to facilitate compatible and lightweight satellite communication facilities.Our work opens up a new avenue for automatic metasurface design and leverages the assemblability to broaden the adaptability of intelligent metadevices.展开更多
Searching for an optimal solution among many nonunique answers provided by transformation optics is critical for many branches of research,such as the burgeoning research on invisibility cloaks.The past decades have w...Searching for an optimal solution among many nonunique answers provided by transformation optics is critical for many branches of research,such as the burgeoning research on invisibility cloaks.The past decades have witnessed rapid development of transformation optics,and different kinds of invisibility cloaks have been designed and implemented.However,the available cloaks realized thus far have been mostly demonstrated with reduced parameters,which greatly impact the predefined cloaking performance.Here,we report a general design strategy to realize full-parameter omnidirectional cloaks that can hide arbitrarily shaped objects in free space.Our approach combines a singular transformation with transformation-invariant metamaterials.The cloaking device with extreme parameters is implemented using a metallic array structure.In the experiment,two cloak samples are designed and fabricated,one with nondiscrete cloaking regions and the other with separated hidden regions.Near-unit transmission of electromagnetic waves with arbitrary incident angles is experimentally demonstrated along with significantly suppressed scattering.Our work challenges the prevailing paradigms of invisibility cloaks and provides deep insight into how transformation optics could be harnessed to obtain easily-accessible metadevices.展开更多
Optical logic operations lie at the heart of optical computing,and they enable many applications such as ultrahighspeed information processing.However,the reported optical logic gates rely heavily on the precise contr...Optical logic operations lie at the heart of optical computing,and they enable many applications such as ultrahighspeed information processing.However,the reported optical logic gates rely heavily on the precise control of input light signals,including their phase difference,polarization,and intensity and the size of the incident beams.Due to the complexity and difficulty in these precise controls,the two output optical logic states may suffer from an inherent instability and a low contrast ratio of intensity.Moreover,the miniaturization of optical logic gates becomes difficult if the extra bulky apparatus for these controls is considered.As such,it is desirable to get rid of these complicated controls and to achieve full logic functionality in a compact photonic system.Such a goal remains challenging.Here,we introduce a simple yet universal design strategy,capable of using plane waves as the incident signal,to perform optical logic operations via a diffractive neural network.Physically,the incident plane wave is first spatially encoded by a specific logic operation at the input layer and further decoded through the hidden layers,namely,a compound Huygens’metasurface.That is,the judiciously designed metasurface scatters the encoded light into one of two small designated areas at the output layer,which provides the information of output logic states.Importantly,after training of the diffractive neural network,all seven basic types of optical logic operations can be realized by the same metasurface.As a conceptual illustration,three logic operations(NOT,OR,and AND)are experimentally demonstrated at microwave frequencies.展开更多
Moving electrons interacting with media can give rise to electromagnetic radiations and has been emerged as a promising platform for particle detection,spectroscopies,and free-electron lasers.In this letter,we investi...Moving electrons interacting with media can give rise to electromagnetic radiations and has been emerged as a promising platform for particle detection,spectroscopies,and free-electron lasers.In this letter,we investigate the Smith-Purcell radiation from helical metagratings,chiral structures similar to deoxyribonucleic acid(DNA),in order to understand the interplay between electrons,photons,and object chirality.Spiral feld patterns can be generated while introducing a gradient azimuthal phase distribution to the induced electric dipole array at the cylindrical interface.Experimental measurements show efcient control over angular momentum of the radiated feld at microwave regime,utilizing a phased electromagnetic dipole array to mimic moving charged particles.Te angular momentum of the radiated wave is determined solely by the handedness of the helical structure,and it thus serves as a potential candidate for the detection of chiral objects.Our fndings not only pave a way for design of orbital angular momentum free-electron lasers but also provide a platform to study the interplay between swif electrons with chiral objects.展开更多
An ideal transformation-based omnidirectional cloak always relies on metamaterials with extreme parameters,which were previously thought to be too difcult to realize.For such a reason,in previous experimental proposal...An ideal transformation-based omnidirectional cloak always relies on metamaterials with extreme parameters,which were previously thought to be too difcult to realize.For such a reason,in previous experimental proposals of invisibility cloaks,the extreme parameters requirements are usually abandoned,leading to inherent scattering.Here,we report on the frst experimental demonstration of an omnidirectional cloak that satisfes the extreme parameters requirement,which can hide objects in a homogenous background.Instead of using resonant metamaterials that usually involve unavoidable absorptive loss,the extreme parameters are achieved using a nonresonant metamaterial comprising arrays of subwavelength metallic channels manufactured with 3D metal printing technology.A high level transmission of electromagnetic wave propagating through the present omnidirectional cloak,as well as signifcant reduction of scattering feld,is demonstrated both numerically and experimentally.Our work may also inspire experimental realizations of the other full-parameter omnidirectional optical devices such as concentrator,rotators,and optical illusion apparatuses.展开更多
基金supported by the National Key Research and Development Program of China (2023YFB4604100, and 2023YFB4604800)the National Natural Science Foundation of China (92163123, 12304492, and 52250191)+1 种基金Zhejiang Provincial Natural Science Foundation of China (LZ24A050002)the China Postdoctoral Science Foundation (2023M733120)。
文摘The paradigm shift of Hermitian systems into the non-Hermitian regime profoundly modifies inherent property of the topological systems, leading to various unprecedented effects such as the nonHermitian skin effect(NHSE). In the past decade, the NHSE has been demonstrated in quantum, optical and acoustic systems. Beside those wave systems, the NHSE in diffusive systems has not yet been observed, despite recent abundant advances in the study of topological thermal diffusion. In this work,we design a thermal diffusion lattice based on a modified Su-Schrieffer-Heeger model and demonstrate the diffusive NHSE. In the proposed model, the asymmetric temperature field coupling inside each unit cell can be judiciously realized by appropriate configurations of structural parameters. We find that the temperature fields trend to concentrate toward the target boundary which is robust against initial excitation conditions. We thus experimentally demonstrated the NHSE in thermal diffusion and verified its robustness against various defects. Our work provides a platform for exploration of non-Hermitian physics in the diffusive systems, which has important applications in efficient heat collection, highly sensitive thermal sensing and others.
基金sponsored by the Key Research and Development Program of the Ministry of Science and Technology under Grants No.2022YFA1404704,2022YFA1404902,2022YFA1405200the National Natural Science Foundation of China(NNSFC)under Grants No.11961141010,No.61975176,the Top-Notch Young Talents Program of China and the Fundamental Research Funds for the Central Universities.
文摘Recent breakthroughs in deep learning have ushered in an essential tool for optics and photonics,recurring in various applications of material design,system optimization,and automation control.Deep learning-enabled on-demand metasurface design has been the subject of extensive expansion,as it can alleviate the time-consuming,low-efficiency,and experience-orientated shortcomings in conventional numerical simulations and physics-based methods.However,collecting samples and training neural networks are fundamentally confined to predefined individual metamaterials and tend to fail for large problem sizes.Inspired by object-oriented C++programming,we propose a knowledge-inherited paradigm for multi-object and shape-unbound metasurface inverse design.Each inherited neural network carries knowledge from the"parent"metasurface and then is freely assembled to construct the"offspring"metasurface;such a process is as simple as building a container-type house.We benchmark the paradigm by the free design of aperiodic and periodic metasurfaces,with accuracies that reach 86.7%.Furthermore,we present an intelligent origami metasurface to facilitate compatible and lightweight satellite communication facilities.Our work opens up a new avenue for automatic metasurface design and leverages the assemblability to broaden the adaptability of intelligent metadevices.
基金sponsored by the Key Research and Development Program of the Ministry of Science and Technology(Grants Nos.2022Y FA1404704,2022YFA1405200,and 2022YFA1404902)the National Natural Science Foundation of China(Grant No.61975176)+5 种基金the Key Research and Development Program of Zhejiang Province(Grant No.2022C01036)the Fundamental Research Funds for the Central Universitiesthe work at Nanyang Technological University was sponsored by Singapore Ministry of Education(Grant No.MOE2018-T2-2-189(S))A*Star AME IRG Grant(Grant No.A20E5c0095)Programmatic Funds(Grant No.A18A7b0058)National Research Foundation Singapore Competitive Research Program(Grant Nos.NRF-CRP22-2019-0006 and NRF-CRP23-2019-0007).
文摘Searching for an optimal solution among many nonunique answers provided by transformation optics is critical for many branches of research,such as the burgeoning research on invisibility cloaks.The past decades have witnessed rapid development of transformation optics,and different kinds of invisibility cloaks have been designed and implemented.However,the available cloaks realized thus far have been mostly demonstrated with reduced parameters,which greatly impact the predefined cloaking performance.Here,we report a general design strategy to realize full-parameter omnidirectional cloaks that can hide arbitrarily shaped objects in free space.Our approach combines a singular transformation with transformation-invariant metamaterials.The cloaking device with extreme parameters is implemented using a metallic array structure.In the experiment,two cloak samples are designed and fabricated,one with nondiscrete cloaking regions and the other with separated hidden regions.Near-unit transmission of electromagnetic waves with arbitrary incident angles is experimentally demonstrated along with significantly suppressed scattering.Our work challenges the prevailing paradigms of invisibility cloaks and provides deep insight into how transformation optics could be harnessed to obtain easily-accessible metadevices.
基金sponsored by the National Natural Science Foundation of China(NNSFC)under Grants Nos.61625502,11961141010,and 61975176the Top-Notch Young Talents Programme of China+4 种基金the Fundamental Research Funds for the Central UniversitiesNanyang Technological University for NAP Start-Up Grantthe Singapore Ministry of Education(Grant Nos.MOE2018-T2-1-022(S),MOE2016-T3-1-006 and Tier 1 RG174/16(S))supported by the Chinese Scholarship Council(CSC No.201906320294)Zhejiang University Academic Award for Outstanding Doctoral Candidates.
文摘Optical logic operations lie at the heart of optical computing,and they enable many applications such as ultrahighspeed information processing.However,the reported optical logic gates rely heavily on the precise control of input light signals,including their phase difference,polarization,and intensity and the size of the incident beams.Due to the complexity and difficulty in these precise controls,the two output optical logic states may suffer from an inherent instability and a low contrast ratio of intensity.Moreover,the miniaturization of optical logic gates becomes difficult if the extra bulky apparatus for these controls is considered.As such,it is desirable to get rid of these complicated controls and to achieve full logic functionality in a compact photonic system.Such a goal remains challenging.Here,we introduce a simple yet universal design strategy,capable of using plane waves as the incident signal,to perform optical logic operations via a diffractive neural network.Physically,the incident plane wave is first spatially encoded by a specific logic operation at the input layer and further decoded through the hidden layers,namely,a compound Huygens’metasurface.That is,the judiciously designed metasurface scatters the encoded light into one of two small designated areas at the output layer,which provides the information of output logic states.Importantly,after training of the diffractive neural network,all seven basic types of optical logic operations can be realized by the same metasurface.As a conceptual illustration,three logic operations(NOT,OR,and AND)are experimentally demonstrated at microwave frequencies.
基金The work at Zhejiang University was sponsored by the National Natural Science Foundation of China under Grants nos.61625502,61574127,61601408,and 61801426the TopNotch Young Talents Program of China,the Fundamental Research Funds for the Central Universities,and the Innovation Joint Research Center for Cyber-Physical-Society System.Te work at Shandong University was sponsored by the National Natural Science Foundation of China under Grant no.61801268the Natural Science Foundation of Shandong Province under Grant no.ZR2018QF001.
文摘Moving electrons interacting with media can give rise to electromagnetic radiations and has been emerged as a promising platform for particle detection,spectroscopies,and free-electron lasers.In this letter,we investigate the Smith-Purcell radiation from helical metagratings,chiral structures similar to deoxyribonucleic acid(DNA),in order to understand the interplay between electrons,photons,and object chirality.Spiral feld patterns can be generated while introducing a gradient azimuthal phase distribution to the induced electric dipole array at the cylindrical interface.Experimental measurements show efcient control over angular momentum of the radiated feld at microwave regime,utilizing a phased electromagnetic dipole array to mimic moving charged particles.Te angular momentum of the radiated wave is determined solely by the handedness of the helical structure,and it thus serves as a potential candidate for the detection of chiral objects.Our fndings not only pave a way for design of orbital angular momentum free-electron lasers but also provide a platform to study the interplay between swif electrons with chiral objects.
基金The authors thank P.Rebusco at Massachusetts Institute of Technology for critical reading and editing of the manuscript.Work in Zhejiang University was sponsored by the National Natural Science Foundation of China under Grants no.61625502,no.61574127,no.61601408,no.61775193,and no.11704332the ZJNSF under Granta no.LY17F010008 and no.LY19F010015+1 种基金the Top-Notch Young Talents Program of China,the Fundamental Research Funds for the Central Universities,and the Innovation Joint Research Center for CyberPhysical-Society.Work at Ames Laboratory was partially supported by the U.S.Department of Energy,Ofce of Basic Energy Science,Division of Materials Sciences and Engineering(Ames Laboratory is operated for the U.S.Department of Energy by Iowa State University under Contract no.DEAC02-07CH11358)Te European Research Council under ERC Advanced Grant no.320081(PHOTOMETA)supported work at FORTH.
文摘An ideal transformation-based omnidirectional cloak always relies on metamaterials with extreme parameters,which were previously thought to be too difcult to realize.For such a reason,in previous experimental proposals of invisibility cloaks,the extreme parameters requirements are usually abandoned,leading to inherent scattering.Here,we report on the frst experimental demonstration of an omnidirectional cloak that satisfes the extreme parameters requirement,which can hide objects in a homogenous background.Instead of using resonant metamaterials that usually involve unavoidable absorptive loss,the extreme parameters are achieved using a nonresonant metamaterial comprising arrays of subwavelength metallic channels manufactured with 3D metal printing technology.A high level transmission of electromagnetic wave propagating through the present omnidirectional cloak,as well as signifcant reduction of scattering feld,is demonstrated both numerically and experimentally.Our work may also inspire experimental realizations of the other full-parameter omnidirectional optical devices such as concentrator,rotators,and optical illusion apparatuses.