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
Since the performance of electronic circuits is becoming rather limited in face of intensively increasing of amount of information and related operations,alloptical processing offers a promising strategy for future in...Since the performance of electronic circuits is becoming rather limited in face of intensively increasing of amount of information and related operations,alloptical processing offers a promising strategy for future information system.It would benefit a great deal if the all-optical processing could be implemented within the developed electronic chips of nanoscale structures.In that it is highly desirable to break the diffraction limit of light for achieving effective light manipulations with deep subwavelength structures compatible with the state-of-the-art nanofabrication processes.It is of fundamental importance to get subwavelength optical localization,that is,squeeze light wave into subwavelength space for achieving freely manipulating of light fields.This review summarizes the development in realizing subwavelength optical localization by exciting toroidal mode in photonic metamaterials.The toroidal excitations in plasmonic metamaterials and Mie resonant metamaterials,in 3D structures and planar metamaterials,with single or few layers in spectral regime from microwave to optical frequencies are surveyed.Based on the discussion on the configurations of toroidal excitations,the recent development on toroidalrelated optical scattering control actively manipulates the toroidal excitations,and promising applications are further investigated and highlighted.展开更多
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.
基金National Natural Science Foundation of China,Grant/Award Numbers:12074314,11774057,11674266,61771402NPU AoXiang New Star programScience,Technology and Innovation Commission of Shenzhen Municipality,Grant/Award Number:JCYJ20170817162221169。
文摘Since the performance of electronic circuits is becoming rather limited in face of intensively increasing of amount of information and related operations,alloptical processing offers a promising strategy for future information system.It would benefit a great deal if the all-optical processing could be implemented within the developed electronic chips of nanoscale structures.In that it is highly desirable to break the diffraction limit of light for achieving effective light manipulations with deep subwavelength structures compatible with the state-of-the-art nanofabrication processes.It is of fundamental importance to get subwavelength optical localization,that is,squeeze light wave into subwavelength space for achieving freely manipulating of light fields.This review summarizes the development in realizing subwavelength optical localization by exciting toroidal mode in photonic metamaterials.The toroidal excitations in plasmonic metamaterials and Mie resonant metamaterials,in 3D structures and planar metamaterials,with single or few layers in spectral regime from microwave to optical frequencies are surveyed.Based on the discussion on the configurations of toroidal excitations,the recent development on toroidalrelated optical scattering control actively manipulates the toroidal excitations,and promising applications are further investigated and highlighted.