As two-dimensional metamaterials, metasurfaces open up new avenues for designing static planar optics. However, the dynamic modulation of metasurfaces in the optical band is required for practical applications. The existing dynamic devices rarely utilized the polarization manipulation capability of metasurfaces. Here, we demonstrate an electrically tunable multifunctional metasurface in the visible range by integrating birefringent liquid crystals (LCs) with all-dielectric metasurfaces based on a novel packaging scheme. By combining the helicity-dependent geometric phase of the metasurface and the polarization control ability of LC molecules, continuous intensity tuning and switching of two helicity channels are realized. Electrically tunable singlechannel switchable metaholograms, multicolor multiplexed metaholograms, and dynamic varifocal metalenses are designed to verify the concept. The exploration of polarization control in dynamic tuning can pave the way for dynamic metasurface devices in various applications, such as space light modulators, light detection and ranging systems, and holographic displays.

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The electromagnetic response of flat metallic surfaces coated with a dielectric grating is studied theoretically. We found that two kinds of optical modes, namely, surface plasmon-polaritons (SPPs) bound to the metallic/grating interfaces and guided modes (GMs) in the dielectric grating, can be excited by externally incident light. Both SPPs and GMs display well-defined band structures due to the introduced periodicity in the dielectric grating.