Reconfigurable dielectric metasurface for active wavefront modulation based on a phase-change material metamolecule design.

Metasurfaces, the promising artificial micro-nano structures with the ability to manipulate the wavefront of light, have been widely studied and reported in recent years. However, dynamic control of the wavefront using dielectric metasurfaces remains a great challenge. Here, unlike the previously reported reconfigurable metasurfaces that offer only binary functions or limited switchable states, we propose and numerically demonstrate an active dielectric metasurface with the metamolecule unit-cell design that enables full-range phase or amplitude tuning in the telecommunications band using the phase-change material GeSbSeTe (GSST). Selective control of the phase transition of each GSST nanopillar in the metamolecule allows multi-level modulation of the phase and amplitude of the light to be achieved. The functionalities of the structure are validated through the generation of optical vortices, phase-only hologram, and pure amplitude modulation. Benefiting from its dynamic wavefront control capability, the proposed metasurface offers major potential for use in future applications including complex beam steering, optical communications, 3D holograms, and displays.