Breaking the Bandwidth Barrier: Graphene‐Driven Programmable Transmissive Metasurfaces Enable Ultra‐Wideband Terahertz Beam Steering

ABSTRACT The recent breakthrough in metasurface technology has introduced a novel paradigm for beam manipulation. However, as operating frequencies extend into the terahertz (THz) band, the intrinsic limitations of conventional tunable devices hinder the bandwidth expansion of THz metasurfaces. This work overcomes the bandwidth bottleneck in THz beam steering by exploiting the ultra‐wideband electromagnetic response enabled by graphene's linear energy‐momentum relationship. We present the first experimental demonstration of independent gain and beam‐steering control using a graphene‐driven transmissive programmable metasurface. By leveraging graphene's inherent broadband properties, we address three key technical challenges: First, a dual‐resonance structure, designed based on coupled‐mode theory, enhances the transmission efficiency of the graphene‐integrated metasurface. Second, a graphene‐insulator‐graphene (GIG) heterostructure replaces ion‐gel‐based gating, thereby avoiding the time‐dependent performance degradation of ion gels and providing a more reliable solution for practical graphene metasurface implementations. Third, a broadband 1‐bit phase coding model is established via a mirror‐operation mode, which effectively mitigates the bandwidth constraints imposed by the non‐uniformity of CVD‐grown graphene on beam steering. The implemented transmissive programmable metasurface, composed of 4,608 unit cells, achieves beam scanning across ±45° from 187 to 250 GHz, corresponding to a 28.8% relative bandwidth‐the highest reported to date. This work not only provides a reconfigurable hardware platform for future 6G communications but also extends the broadband control mechanism to multidimensional parameter manipulation, including amplitude, polarization, and orbital angular momentum.