Graphene-integrated meta-lens for tunable terahertz wave focusing

We propose a graphene-integrated geometric-phase metasurface designed for a terahertz meta-lens that features dynamic tunability in both intensity and focal length. By rotating the metasurface unit cells, we adjust the phase profile based on the Pancharatnam-Berry (PB) phase principle, achieving a focal length modulation range from 1,800 μm to 2,400 μm. By electrical tuning of the graphene Fermi level from 0 eV to 1 eV enables over 70% intensity variation in focusing. Fullwave simulations demonstrate efficient polarization conversion, with conversion rates exceeding 80% across the 0.9–1.1 THz frequency band. This work presents a compact and versatile solution for reconfigurable terahertz imaging systems.