Control of the harmonic near-field distributions by an active metasurface loaded with pin diodes
Jin Yang, Jun Ke, Mao Chen, Ming Zheng Chen, Jun Yan Dai, Jianfeng Chen, Rui Yang, Jun Wu, Qiang Cheng, Tie Jun Cui
Abstract
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-time-digital coding metasurface to realize accurate manipulation of the near fields at the fundamental and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m1"> <mml:mrow> <mml:mo form="prefix">+</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:math> st ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m2"> <mml:mrow> <mml:mo form="prefix">−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:math> 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.