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.

Jun Chen Ke;Jun Yan Dai;Jun Wei Zhang;Zhanye Chen;Ming Zheng Chen;Yunfeng Lu;Lei Zhang;Li Wang;Qun Yan Zhou;Long Li;Jin Shan Ding;Qiang Cheng;Tie Jun Cui

Institute of Electromagnetic Space,Southeast University,210096 Nanjing,China;State Key Laboratory of Millimeter Waves,Southeast University,210096 Nanjing,China;School of Electronic Engineering,Xidian University,710071 Xi'an,China

光：科学与应用（英文版）

[1]Jun Chen Ke;Jun Yan Dai;Jun Wei Zhang;Zhanye Chen;Ming Zheng Chen;Yunfeng Lu;Lei Zhang;Li Wang;Qun Yan Zhou;Long Li;Jin Shan Ding;Qiang Cheng;Tie Jun Cui-.Frequency-modulated continuous waves controlled by space-time-coding metasurface with nonlinearly periodic phases)[J].光：科学与应用（英文版）,2022(10):2424-2434

STCMs,STCM,FMCWs,reprogrammable

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