Ultrafast polarization-dependent all-optical switching of germanium-based metaphotonic devices

Metamaterials play an important role in the modulation of amplitude and group delay in the terahertz (THz) regime on account of their optical properties, which are rare in natural materials. Here an ultrafast anisotropic switch of the plasmon- induced transparency (PIT) effect is experimentally and numerically demonstrated by metamaterial devices composed of two pairs of planar split-ring resonators and a pair of closed-ring resonators. By integration with a germanium (Ge) film, a recovery time of 3 ps and a decay constant of 785 fs are realized in the metadevice. Stimulated by the exterior optical pump, the PIT windows at different frequencies are switched off with an excellent property of slow light for vertical and horizontal THz polarizations, realizing an astonishing modulation depth as high as 99.06%. This work provides a new platform for ultrafast anisotropic metadevices tunable for amplitude and group delay. (C) 2020 Chinese Laser Press