All‐Optical and Ultrafast Tuning of Terahertz Plasmonic Metasurfaces

Abstract Metasurfaces have been widely used to manipulate terahertz waves due to their great potential for achieving unique electromagnetic responses. However, to realize ultrafast and efficient control of the light in active metasurfaces is still a critical challenge. Here, an ultrafast tunable metasurface which consists of ion‐implanted and annealed silicon disk array is experimentally demonstrated in the terahertz range. By utilizing the optical‐pump terahertz‐probe spectroscopy, the absolute transmission modulation up to 38% is realized at the electric dipole resonance under the femtosecond pulse excitation, with a switch‐on time within 20 ps and a recovery time of 300 ps. Furthermore, a theoretical analysis that quantitatively models the time dependence of the electron–hole plasma density and the permittivity of the silicon disks is proposed. Then, the transient transmission spectra of the metasurface are numerically simulated, which agree well with the experimental performances. The silicon‐based metasurface shows significant potential in ultrafast terahertz optics.