Broadband and optically tunable terahertz metasurface absorber based on intrinsic silicon

Abstract With the gradual advancement of various application technologies of terahertz waves, efficient absorption and shielding have become essential research priorities. Metasurface absorbers offer significant advantages, such as customizable frequency bands and multifunctional integration. This article presents a novel all-silicon metasurface designed for optically tunable and ultra-broadband terahertz wave absorption. By incorporating diverse electromagnetic resonance modes into the meta-atoms, multiple low-reflection peaks are generated, thereby extending the operational bandwidth. Utilizing the specific photon energy of a near-infrared (1064 nm) continuous-wave laser, widely distributed photogenerated carriers are formed across the entire device thickness, increasing the dissipation distance of terahertz waves and achieving high absorption efficiency. Simulation and experimental results demonstrate that the proposed metasurface absorber achieves an effective bandwidth of 2.1 THz (0.5–2.6 THz), with an incident angle tolerance exceeding 70° at certain frequencies. Under infrared laser illumination, the absorption efficiency switches effectively from 0 to 99.9%, while the entire device remains as thin as 500 μm. This design provides a new approach for developing tunable terahertz absorbers.