Photogenerated metasurfaces at terahertz frequencies induced by a continuous-wave low pump

Active metasurfaces have attracted a great deal of attention due to the unlimited ways of controlling electromagnetic radiation. In this work, we theoretically study the THz electromagnetic properties of photogenerated metasurfaces in an InAs slab. We use a spatially modulated optical pump to modify the permittivity. Those modifications are calculated by solving the ambipolar rate equation for the photocarriers. This work reveals the crucial impact of the photocarrier diffusion for realizing optimal metasurfaces for the control of THz radiation. We demonstrate that InAs is a promising semiconductor that could be used to manufacture fast and efficient on-chip THz components. We also demonstrate that low pump fluence in the continuous regime of only tens of $\text{W}\phantom{\rule{0.16em}{0ex}}{\text{cm}}^{\ensuremath{-}2}$ is sufficient to modulate the absorption of the THz waves up to $67%$ over a broad frequency range from 1 to 3 THz.