The rapid development of space-time-coding metasurfaces(STCMs)offers a new avenue to manipulate spatial electromagnetic beams,waveforms,and frequency spectra simultaneously with high efficiency.To date,most studies ar...The rapid development of space-time-coding metasurfaces(STCMs)offers a new avenue to manipulate spatial electromagnetic beams,waveforms,and frequency spectra simultaneously with high efficiency.To date,most studies are primarily focused on harmonic generations and independent controls of finite-order harmonics and their spatial waves,but the manipulations of continuously temporal waveforms that include much rich frequency spectral components are still limited in both theory and experiment based on STCM.Here,we propose a theoretical framework and method to generate frequency-modulated continuous waves(FMCWs)and control their spatial propagation behaviors simultaneously via a novel STCM with nonlinearly periodic phases.Since the carrier frequency of FMCW changes with time rapidly,we can produce customized time-varying reflection phases at will by the required FMCW under the illumination of a monochromatic wave.More importantly,the propagation directions of the time-varying beams can be controlled by encoding the metasurface with different initial phase gradients.A programmable STCM prototype with a full-phase range is designed and fabricated to realize reprogrammable FMCW functions,and experimental results show good agreement with the theoretical analyses.展开更多
Recent advances of space-time-coding digital metasurfaces demonstrate powerful capabilities in the generation of nonlinear harmonics and the accurate control of the corresponding wavefronts. However, to date the near ...Recent advances of space-time-coding digital metasurfaces demonstrate powerful capabilities in the generation of nonlinear harmonics and the accurate control of the corresponding wavefronts. However, to date the near field manipulation and the experiment characterization are still not explored. In this paper, we propose a space-timedigital coding metasurface to realize accurate manipulation of the near fields at the fundamental and +1 st(-1 st)harmonics simultaneously, by properly controlling the initial phase and time delay of the time varying reflectivity.A novel mapping system is established to measure the nonlinear near field distributions of multiharmonics. Both the simulation and experimental results demonstrate the validity of the proposed method.展开更多
基金This work was supported by the Basic Scientific Center of Information Metamaterials of the National Natural Science Foundation of China(6228810001)the National Key Research and Development Program of China(2017YFA0700201,2017YFA0700202,2017YFA0700203,and 2018YF A0701904)+3 种基金the National Natural Science Foundation of China(61722106 and 61731010)the Major Project of Natural Science Foundation of Jiangsu Province(BK20212002)the 111 Project(111-2-05)the China Postdoctoral Science Foundation(2020M680062).
文摘The rapid development of space-time-coding metasurfaces(STCMs)offers a new avenue to manipulate spatial electromagnetic beams,waveforms,and frequency spectra simultaneously with high efficiency.To date,most studies are primarily focused on harmonic generations and independent controls of finite-order harmonics and their spatial waves,but the manipulations of continuously temporal waveforms that include much rich frequency spectral components are still limited in both theory and experiment based on STCM.Here,we propose a theoretical framework and method to generate frequency-modulated continuous waves(FMCWs)and control their spatial propagation behaviors simultaneously via a novel STCM with nonlinearly periodic phases.Since the carrier frequency of FMCW changes with time rapidly,we can produce customized time-varying reflection phases at will by the required FMCW under the illumination of a monochromatic wave.More importantly,the propagation directions of the time-varying beams can be controlled by encoding the metasurface with different initial phase gradients.A programmable STCM prototype with a full-phase range is designed and fabricated to realize reprogrammable FMCW functions,and experimental results show good agreement with the theoretical analyses.
基金111 Project (111-2-05)National Natural Science Foundation of China (11227904, 61722106,61731010)National Key Research and Development Program of China (2017YFA0700201, 2017YFA0700202,2017YFA0700203, 2018YFA0701904)。
文摘Recent advances of space-time-coding digital metasurfaces demonstrate powerful capabilities in the generation of nonlinear harmonics and the accurate control of the corresponding wavefronts. However, to date the near field manipulation and the experiment characterization are still not explored. In this paper, we propose a space-timedigital coding metasurface to realize accurate manipulation of the near fields at the fundamental and +1 st(-1 st)harmonics simultaneously, by properly controlling the initial phase and time delay of the time varying reflectivity.A novel mapping system is established to measure the nonlinear near field distributions of multiharmonics. Both the simulation and experimental results demonstrate the validity of the proposed method.
