Crosstalk-free dual-channel amplitude-phase control in a gate tunable graphene THz metasurface

Graphene-based terahertz (THz) metasurfaces offer compact, electrically tunable wavefront control for communications and secure photonics. Yet, crosstalk-free tuning of amplitude and phase within a single device has remained a central challenge. Here, we report a graphene-based THz metasurface composed of a unit cell with five-fold rotational symmetry ( C 5 ), enabling crosstalk-free and independent control of transmission amplitude and phase by tuning the gate voltage. The C 5 unit cell produces a nearly isotropic angular harmonic distribution, imparting polarization insensitivity and wide-angle stability. Experiments and simulations indicate that, under low gate bias, the metasurface achieves 25% modulation of transmission amplitude in the co-polarized channel while maintaining an unchanged phase spectrum. An extinction ratio exceeding 40 dB between co- and cross-polarized transmissions confirms its high polarization purity. In the cross-polarized channel, continuous phase shifts exceeding 180 deg are realized across multiple frequency bands while maintaining ultralow transmission amplitude, indicating that phase control is gate-programmable and effectively decoupled from the co-polarized channel amplitude output. To our knowledge, our results establish a new design paradigm for electrically programmable metasurfaces with crosstalk-free control, opening avenues for applications in optoelectronic modulation and key-distribution channels.