Light trapping is a constant pursuit in photonics because of its importance in science and technology.Many mechanisms have been explored,including the use of mirrors made of materials or structures that forbid outgoin...Light trapping is a constant pursuit in photonics because of its importance in science and technology.Many mechanisms have been explored,including the use of mirrors made of materials or structures that forbid outgoing waves,and bound states in the continuum that are mirror-less but based on topology.Here we report a compound method,combining lateral mirrors and bound states in the continuum in a cooperative way,to achieve a class of on-chip optical cavities that have high quality factors and small modal volumes.Specifically,light is trapped in the transverse direction by the photonic band gap of the lateral hetero-structure and confined in the vertical direction by the constellation of multiple bound states in the continuum.As a result,unlike most bound states in the continuum found in photonic crystal slabs that are de-localized Bloch modes,we achieve light-trapping in all three dimensions and experimentally demonstrate quality factors as high as Q=1.09×10^(6)and modal volumes as low as V=17.74(λ_(0)/n)^(3)in the telecommunication regime.We further prove the robustness of our method through the statistical study of multiple fabricated devices.Our work provides a new method of light trapping,which can find potential applications in photonic integration,nonlinear optics and quantum computing.展开更多
Topological photonic states have promising applications in slow light,photon sorting,and optical buffering.However,realizing such states in non-Hermitian systems has been challenging due to their complexity and elusiv...Topological photonic states have promising applications in slow light,photon sorting,and optical buffering.However,realizing such states in non-Hermitian systems has been challenging due to their complexity and elusive properties.In this work,we have experimentally realized a topological rainbow in non-Hermitian photonic crystals by controlling loss in the microwave frequency range for what we believe is the first time.We reveal that the lossy photonic crystal provides a reliable platform for the study of non-Hermitian photonics,and loss is also taken as a degree of freedom to modulate topological states,both theoretically and experimentally.This work opens a way for the construction of a nonHermitian photonic crystal platform,will greatly promote the development of topological photonic devices,and will lay a foundation for the real-world applications.展开更多
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 operations.All-optical logic gates have been dem...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 operations.All-optical logic gates have been demonstrated based on conventional waveguides and interferometry,as well as photonic crystal structures.Nonetheless,any defects in those structures will introduce high scattering loss,which compromises the fidelity and contrast ratio of the information process.Based 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 structure.By tuning the working bandwidth of the two input channels,we prevent interference between the two channels to achieve a stable and high-fidelity output.The transmittance of both channels is higher than 0.8,and a high contrast ratio of 28.8 dB is achieved.Moreover,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 computing.The device’s footprint is 18μm×12μm,allowing high-density on-chip integration.In addition,this design can be experimentally fabricated using current nanofabrication techniques and will have potential applications in optical communication,information processing,and quantum computing.展开更多
Antichiral gyromagnetic photonic crystal(GPC)in a honeycomb lattice with the two interpenetrating triangular sublattices A and B magnetically biased in opposite directions can realize antichiral one-way edge states pr...Antichiral gyromagnetic photonic crystal(GPC)in a honeycomb lattice with the two interpenetrating triangular sublattices A and B magnetically biased in opposite directions can realize antichiral one-way edge states propagating along the same direction at its two parallel edges.Here,we report the construction and observation of topological beam splitting with the easily adjustable right-to-left ratio in an antichiral GPC.The splitter is compact and configurable,has high trans-mission efficiency,and allows for multi-channel utilization,crosstalk-proof,and robust against defects and obstacles.This magnificent performance is attributed to the peculiar property that antichiral one-way edge states exist only at zigzag edge but not at armchair edge of antichiral GPC.When we combine two rectangular antichiral GPCs holding left-and right-propagating antichiral one-way edge states respectively,bidirectionally radiating one-way edge states at two paral-lel zigzag edges can be achieved.Our observations can enrich the understanding of fundamental physics and expand to-pological photonic applications.展开更多
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 chi...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 anomalies.Type-I Weyl systems possess a complete bandgap,and topologically protected surface states can be excited without disturbing the bulk states.In 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 crystal.We propose a new strategy to construct a type-I Weyl system by stacking the hexagonal photonic lattice.Different 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 layers.We 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 sites.The surface states at opposite boundaries of the proposed system have opposite group velocities,which is the feature of type-I Weyl points.Our study provides a new method of exploring topologically protected photonic systems and developing possible topological devices.展开更多
基金partly supported by the National Natural Science Foundation of China(61922004 and 62135001)the National Key Research and Development Program of China(2020YFB1806405)+4 种基金the Major Key Project of PCL(PCL2021A14)the Open Fund of the State Key Laboratory of Integrated OptoelectronicsUS National Science Foundation through the University of Pennsylvania Material Research Science and Engineering Center(DMR-1720530)US Office of Naval Research(ONR)Multidisciplinary University Research Initiative(MURI)Grant N00014-20-1-2325 on Robust Photonic Materials with High-Order Topological Protectionthe US Army Research Office under award contract W911-NF-19-1-0087。
文摘Light trapping is a constant pursuit in photonics because of its importance in science and technology.Many mechanisms have been explored,including the use of mirrors made of materials or structures that forbid outgoing waves,and bound states in the continuum that are mirror-less but based on topology.Here we report a compound method,combining lateral mirrors and bound states in the continuum in a cooperative way,to achieve a class of on-chip optical cavities that have high quality factors and small modal volumes.Specifically,light is trapped in the transverse direction by the photonic band gap of the lateral hetero-structure and confined in the vertical direction by the constellation of multiple bound states in the continuum.As a result,unlike most bound states in the continuum found in photonic crystal slabs that are de-localized Bloch modes,we achieve light-trapping in all three dimensions and experimentally demonstrate quality factors as high as Q=1.09×10^(6)and modal volumes as low as V=17.74(λ_(0)/n)^(3)in the telecommunication regime.We further prove the robustness of our method through the statistical study of multiple fabricated devices.Our work provides a new method of light trapping,which can find potential applications in photonic integration,nonlinear optics and quantum computing.
基金supported by the National Natural Science Foundation of China(Nos.12274031,12274315,92050110,11734001,91950204,and 92150302)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)+1 种基金the National Key Research and Development Program of China(No.2018YFB2200403)the Beijing Institute of Technology Research Fund Program for Teli Young Fellows,and the Beijing Institute of Technology Science and Technology Innovation Plan Innovative Talents Science and Technology Funding Special Plan(No.2022CX01006).
文摘Topological photonic states have promising applications in slow light,photon sorting,and optical buffering.However,realizing such states in non-Hermitian systems has been challenging due to their complexity and elusive properties.In this work,we have experimentally realized a topological rainbow in non-Hermitian photonic crystals by controlling loss in the microwave frequency range for what we believe is the first time.We reveal that the lossy photonic crystal provides a reliable platform for the study of non-Hermitian photonics,and loss is also taken as a degree of freedom to modulate topological states,both theoretically and experimentally.This work opens a way for the construction of a nonHermitian photonic crystal platform,will greatly promote the development of topological photonic devices,and will lay a foundation for the real-world applications.
基金Project supported by the National Key Research and Development Program of the Ministry of Science and Technology of China(Grant No.2022YFA1404201)the National Natural Science Foundation of China(Grant No.11904255)the Key Research and Development Program of Shanxi Province(International Cooperation)(Grant No.201903D421052).
文摘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 operations.All-optical logic gates have been demonstrated based on conventional waveguides and interferometry,as well as photonic crystal structures.Nonetheless,any defects in those structures will introduce high scattering loss,which compromises the fidelity and contrast ratio of the information process.Based 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 structure.By tuning the working bandwidth of the two input channels,we prevent interference between the two channels to achieve a stable and high-fidelity output.The transmittance of both channels is higher than 0.8,and a high contrast ratio of 28.8 dB is achieved.Moreover,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 computing.The device’s footprint is 18μm×12μm,allowing high-density on-chip integration.In addition,this design can be experimentally fabricated using current nanofabrication techniques and will have potential applications in optical communication,information processing,and quantum computing.
基金the National Natural Science Foundation of China(11974119)Science and Technology Project of Guangdong(2020B010190001)+1 种基金Guangdong Innovative and Entrepreneurial Research Team Program(2016ZT06C594)National Key R&D Program of China(2018YFA 0306200).
文摘Antichiral gyromagnetic photonic crystal(GPC)in a honeycomb lattice with the two interpenetrating triangular sublattices A and B magnetically biased in opposite directions can realize antichiral one-way edge states propagating along the same direction at its two parallel edges.Here,we report the construction and observation of topological beam splitting with the easily adjustable right-to-left ratio in an antichiral GPC.The splitter is compact and configurable,has high trans-mission efficiency,and allows for multi-channel utilization,crosstalk-proof,and robust against defects and obstacles.This magnificent performance is attributed to the peculiar property that antichiral one-way edge states exist only at zigzag edge but not at armchair edge of antichiral GPC.When we combine two rectangular antichiral GPCs holding left-and right-propagating antichiral one-way edge states respectively,bidirectionally radiating one-way edge states at two paral-lel zigzag edges can be achieved.Our observations can enrich the understanding of fundamental physics and expand to-pological photonic applications.
基金supported by the Beijing Outstanding Young Scientist Program(Grant No.BJJWZYJH01201910007022)the National Natural Science Foundation of China(Grant Nos.61775019,and 92050117)the National Postdoctoral Program for Innovative Talents of China(Grant No.BX20200050)。
文摘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 anomalies.Type-I Weyl systems possess a complete bandgap,and topologically protected surface states can be excited without disturbing the bulk states.In 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 crystal.We propose a new strategy to construct a type-I Weyl system by stacking the hexagonal photonic lattice.Different 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 layers.We 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 sites.The surface states at opposite boundaries of the proposed system have opposite group velocities,which is the feature of type-I Weyl points.Our study provides a new method of exploring topologically protected photonic systems and developing possible topological devices.
