Research on full-polarization electromagnetic holographic imaging based on quasi-symmetrical structure reconfigurable metasurfaces

In the paper, a quasi-symmetrical structure reconfigurable metasurfaces (QSRMS) is proposed to generate the full-polarization electromagnetic (EM) holographic imaging. A combination of metasurfaces and varactor that involves the position and the gap of loading varactor is explored to achieve low-loss characteristics. The loading of the capacitor allows the element of reconfigurable metasurfaces (RMS) to present quasi-central symmetry, thus reducing the coupling between co- and cross-polarization. Therefore, the phase shift of 310 degrees and the amplitude loss of 1.3 dB in the two orthogonal directions are acquired at 5.2 GHz. And the 3dB-loss bandwidth reaches 15.67%. Based on the dual-polarization QSRMS, the amplitude and phase modulation (APM) of the EM field are implemented simultaneously using L-BFGS-B algorithm. The implementation process of holographic imaging shows that all polarization state of the Poincare sphere can be realized by designing the phase distribution of the QSRMS. Furthermore, the multi-polarization multiplexing holographic imaging is also investigated in this research, indicating that the polarization carrying capacity (PCC) can be enhanced by increasing the aperture of the metasurfaces. The results of simulation and experiment reveal that there will be a broad application prospect in next-generation large-scale, multi-channel EM intellisense systems. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement