One- and two-dimensional photo-imprinted diffraction gratings for   manipulating terahertz waves
  Emerging technology based on artificial materials containing metallic structures has raised the prospect for unprecedented control of terahertz waves through components like filters, absorbers and polarizers. The functionality of these devices is static by the very nature of their metallic or polaritonic composition, although some degree of tunability can be achieved by incorporating electrically biased semiconductors. Here, we demonstrate a photonic structure by projecting the optical image of a metal mask onto a thin GaAs substrate using a femtosecond pulsed laser source. We show that the resulting high-contrast pattern of photo- excited carriers can create diffractive elements operating in transmission. With the metal mask replaced by a digital micromirror device, our photo-imprinted photonic structures provide a route to terahertz components with reconfigurable functionality. 
Ioannis Chatzakis, Philippe Tassin, Liang Luo, Nian-Hai Shen, Lei   Zhang, Jigang Wang, Thomas Koschny, and Costas M. Soukoulis
physics.optics