Ultrafast control of slow light in THz electromagnetically induced transparency metasurfaces

In this paper, we experimentally demonstrate ultrafast optical control of slow light in the terahertz (THz) range by combining the electromagnetically induced transparency (EIT) metasurfaces with the cut wire made of P +-implanted silicon with short carrier lifetime. Employing the optical-pump THz-probe spectroscopy, we observed that the device transited from a state with a slow light effect to a state without a slow light effect in an ultrafast time of 5 ps and recovered within 200 ps. A coupled oscillator model is utilized to explain the origin of controllability. The experimental results agree very well with the simulated and theoretical results. These EIT metasurfaces have the potential to be used as an ultrafast THz optical delay device.