Dynamic Transmissive Metasurface for Broadband Phase‐Only Modulation Based on Phase‐Change Materials

Abstract Dynamic metasurfaces provide exciting opportunities for spatial light modulation with ultra‐compact footprint and high resolution. Designs reported so far typically suffer from efficiency problem due to the strong coupling between amplitude and phase modulation. Huygens metasurface design eliminates the back propagation with interference of dual resonances, offering a potential solution for phase‐only modulation. However, the intrinsic dispersion mismatch between the dual modes restricts this design to a highly limited bandwidth. Here, a dynamic phase‐change metasurface design that enables transmissive phase modulation covering over 240° with high‐level transmisstance maintained over 0.8 and a large operation bandwidth of 80 nm ranging from 1516 to 1596 nm, is presented. To verify the potential usage of this design, a multi‐state phase‐change control scheme that enables quasi‐continuous phase modulation is further provided. The key feature of this design is the leverage of congener Huygens concept. Judicious incorporation of lossless phase‐change material (PCM) with congener Huygens metasurface allows wideband holding of Huygens condition, which provides a perfect platform to simultaneously address the efficiency and bandwidth problems. This novel feature represents a meaningful step forward to integrate spatial light modulation.