▎ 摘　　要

Dynamic phase modulation of electromagnetic waves is desirable in many applications such as beaming, tunable focusing, and holography. However, it remains challenging to achieve both large dynamic phase shift and high transmittance based on terahertz metamaterials. Here we propose a double-layered graphene-metal metamaterial for achieving transmissive terahertz phase modulator with large dynamic phase modulation range and meanwhile high transmittance. Numerical results show that a large dynamic transmission phase shift reaching up to 180(circle) and relatively high transmittance above 22% can be achieved simultaneously by varying the graphene Fermi level from 0 to 1 eV. We attribute this striking performance to the transition of the resonance type when the graphene Fermi level is tuned across a threshold. We expect that the proposed dynamic phase modulator will find applications in the tunable lens, holographic imaging and phased array antenna in terahertz regime.