Spatiotemporal Metasurface to Control Electromagnetic Wave Scattering

Metasurfaces, the artificially planar electromagnetic structures, have exhibited strong potential for arbitrary electromagnetic wave-scattering control; however, most of the existing low-scattering metasurfaces are based on spatial phase redistributions to generate diffusive backscattering, leaving time dimension unexploited. The time-modulated mechanism provides an attractive alternative to realize backscattering control but still lacks experimental demonstration for realization of radar cross-section reduction in microwave frequencies. Here, we propose a broadband spatiotemporal metasurface approach for arbitrary scattering control and provide experimental evidence of reshaping scattering patterns in the spatial and spectral domains simultaneously. The metasurface is composed of broadband high-efficiency meta-atoms incorporating electric p-i-n diodes, which ensures independent and dynamic phase-response modulation over time under external voltage control in an octave working band from 3.4 to 7.7 GHz. The measured results demonstrate that the metasurface could redirect incidence to various spatial directions and harmonic frequencies, achieving broadband spatial and spectral control of the backward scattering. The proposed metasurface may offer promising applications in radar detection and camouflage.