Manipulating circularly polarized(CP)electromagnetic(EM)waves at will is significantly important for a wide range of applications ranging from chiral-molecule manipulations to optical communication.However,conventiona...Manipulating circularly polarized(CP)electromagnetic(EM)waves at will is significantly important for a wide range of applications ranging from chiral-molecule manipulations to optical communication.However,conventional EM devices based on natural materials suffer from limited functionalities,bulky configurations,and low efficiencies.Recently,Pancharatnam-Berry(PB)phase metasurfaces have shown excellent capabilities in controlling CP waves in different frequency domains,thereby allowing for multi-functional PB meta-devices that integrate distinct functionalities into single and flat devices.Nevertheless,the PB phase has intrinsically opposite signs for two spins,resulting in locked and mirrored functionalities for right CP and left CP beams.Here we review the fundamentals and applications of spin-decoupled metasurfaces that release the spin-locked limitation of PB metasurfaces by combining the orientation-dependent PB phase and the dimension-dependent propagation phase.This provides a general and practical guideline toward realizing spin-decoupled functionalities with a single metasurface for orthogonal circular polarizations.Finally,we conclude this review with a short conclusion and personal outlook on the future directions of this rapidly growing research area,hoping to stimulate new research outputs that can be useful in future applications.展开更多
Recently,the metasurfaces for independently controlling the wavefront and amplitude of two orthogonal circularly polarized electromagnetic(EM)waves have been demonstrated to open a way toward spin-multiplexing compact...Recently,the metasurfaces for independently controlling the wavefront and amplitude of two orthogonal circularly polarized electromagnetic(EM)waves have been demonstrated to open a way toward spin-multiplexing compact metadevices.However,these metasurfaces are mostly restricted to a single operation frequency band.The main challenge to achieving multiple frequency manipulations stems from the complicated and time-consuming design caused by multifrequency cross talk.To solve this problem,we propose a deep-learning-assisted inverse design method for designing a dual-spin/frequency metasurface with flexible multiplexing of off-axis vortices.By analyzing the cross talk between different spin/frequency channels based on the deep-learning method,we established the internal mapping relationship between the physical parameters of a meta-atom and its phase responses in multichannels,realizing the rapid inverse design of the spin/frequency multiplexing EM device.As a proof of concept,we demonstrated in the microwave region a dual-frequency arbitrary spin-to-orbit angular momentum converter,a dual-frequency off-axis vector vortex multiplexer,and a large-capacity(16-channel)vortex beam generator.The proposed method may provide a compact and efficient platform for the multiplexing of vortices,which may further stimulate their applications in wireless communication and quantum information science.展开更多
The wavefront control of spin or orbital angular momentum(OAM)is widely applied in the optical and radio fields.However,most passive metasurfaces provide limited manipulations,such as the spin-locked wavefront,a stati...The wavefront control of spin or orbital angular momentum(OAM)is widely applied in the optical and radio fields.However,most passive metasurfaces provide limited manipulations,such as the spin-locked wavefront,a static OAM combination,or an uncontrollable OAM energy distribution.We propose a reflection-type multi-feed metasurface to independently generate multi-mode OAM beams with dynamically switchable OAM combinations and spin states,while simultaneously,the energy distribution of carrying OAM modes is controllable.Specifically,four elements are proposed to overcome the spin-locked phase limitation by combining propagation and geometric phases.The robustness of these elements is analyzed.By involving the amplitude term and multi-feed technology in the design process,the proposed metasurface can generate OAM beams with a controllable energy distribution over modes and switchable mode combinations.OAM-based radio communication with four independent channels is experimentally demonstrated at 14 GHz by employing a pair of the proposed metasurfaces.The powers of different channels are adjustable by the provided amplitude term,and the maximum crosstalk is−9 dB,proving the effectiveness and practicability of the proposed method.展开更多
基金the support from the National Natural Science Foundation of China(Grant No.11604167)Zhejiang Province Natural Science Foundation of China(No.LY19A040004)F.Ding acknowledges the support from Villum Fonden(Nos.00022988 and 37372).
文摘Manipulating circularly polarized(CP)electromagnetic(EM)waves at will is significantly important for a wide range of applications ranging from chiral-molecule manipulations to optical communication.However,conventional EM devices based on natural materials suffer from limited functionalities,bulky configurations,and low efficiencies.Recently,Pancharatnam-Berry(PB)phase metasurfaces have shown excellent capabilities in controlling CP waves in different frequency domains,thereby allowing for multi-functional PB meta-devices that integrate distinct functionalities into single and flat devices.Nevertheless,the PB phase has intrinsically opposite signs for two spins,resulting in locked and mirrored functionalities for right CP and left CP beams.Here we review the fundamentals and applications of spin-decoupled metasurfaces that release the spin-locked limitation of PB metasurfaces by combining the orientation-dependent PB phase and the dimension-dependent propagation phase.This provides a general and practical guideline toward realizing spin-decoupled functionalities with a single metasurface for orthogonal circular polarizations.Finally,we conclude this review with a short conclusion and personal outlook on the future directions of this rapidly growing research area,hoping to stimulate new research outputs that can be useful in future applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.62271243 and 62071215)the National Key Research and Development Program of China(Grant No.2017YFA0700201)+1 种基金the Joint Fund of Ministry of Education for Equipment Pre-research(Grant No.8091B032112)the Priority Academic Program Development of Jiangsu Higher Education Institutions,the Fundamental Research Funds for the Central Universities,and Jiangsu Provincial Key Laboratory of Advanced Manipulating Technique of Electromagnetic Wave.
文摘Recently,the metasurfaces for independently controlling the wavefront and amplitude of two orthogonal circularly polarized electromagnetic(EM)waves have been demonstrated to open a way toward spin-multiplexing compact metadevices.However,these metasurfaces are mostly restricted to a single operation frequency band.The main challenge to achieving multiple frequency manipulations stems from the complicated and time-consuming design caused by multifrequency cross talk.To solve this problem,we propose a deep-learning-assisted inverse design method for designing a dual-spin/frequency metasurface with flexible multiplexing of off-axis vortices.By analyzing the cross talk between different spin/frequency channels based on the deep-learning method,we established the internal mapping relationship between the physical parameters of a meta-atom and its phase responses in multichannels,realizing the rapid inverse design of the spin/frequency multiplexing EM device.As a proof of concept,we demonstrated in the microwave region a dual-frequency arbitrary spin-to-orbit angular momentum converter,a dual-frequency off-axis vector vortex multiplexer,and a large-capacity(16-channel)vortex beam generator.The proposed method may provide a compact and efficient platform for the multiplexing of vortices,which may further stimulate their applications in wireless communication and quantum information science.
基金Project supported by the National Natural Science Foundation of China(Nos.61971115,61721001,61975177,61971099)。
文摘The wavefront control of spin or orbital angular momentum(OAM)is widely applied in the optical and radio fields.However,most passive metasurfaces provide limited manipulations,such as the spin-locked wavefront,a static OAM combination,or an uncontrollable OAM energy distribution.We propose a reflection-type multi-feed metasurface to independently generate multi-mode OAM beams with dynamically switchable OAM combinations and spin states,while simultaneously,the energy distribution of carrying OAM modes is controllable.Specifically,four elements are proposed to overcome the spin-locked phase limitation by combining propagation and geometric phases.The robustness of these elements is analyzed.By involving the amplitude term and multi-feed technology in the design process,the proposed metasurface can generate OAM beams with a controllable energy distribution over modes and switchable mode combinations.OAM-based radio communication with four independent channels is experimentally demonstrated at 14 GHz by employing a pair of the proposed metasurfaces.The powers of different channels are adjustable by the provided amplitude term,and the maximum crosstalk is−9 dB,proving the effectiveness and practicability of the proposed method.
