Design of metasurfaces with decoupled amplitude and phase response for spatial light modulation

Spatial light modulators based on metasurfaces have attracted great attention due to their abilities of amplitude and phase modulation. However, the traditional one degree of freedom (1-DOF) tunable metasurfaces are limited by incomplete phase coverage and coupled amplitude and phase modulation. Here, we propose an optimization method for 2-DOF tunable metasurfaces within the framework of temporal coupled mode theory. As a validation of the proposed method, we present a germanium antimony tellurium (GST)-alloy-based 2-DOF tunable reflective metasurface. Full-wave simulation shows that independent modulation of amplitude and phase is realized with full phase coverage and amplitude range from 0 to 0.55. Our proposed design scheme for a 2-DOF tunable metasurface may facilitate the development of high-performance metasurface devices.