Extrinsic electromagnetic chirality in all-photodesigned one-dimensional terahertz metamaterials

We suggest that all-photodesigned metamaterials, subwavelength custom patterns of photoexcited carriers on a semiconductor, can display an exotic extrinsic electromagnetic chirality in the terahertz (THz) frequency range. We consider a photoinduced pattern exhibiting one-dimensional geometrical chirality, i.e., its mirror image cannot be superposed onto itself by translations without rotations, and in the long wavelength limit we evaluate its bianisotropic response. The photoinduced extrinsic chirality turns out to be fully reconfigurable by recasting the optical illumination which supports the photoexcited carriers. The all-photodesigning technique represents a feasible, easy, and powerful method for achieving effective matter functionalization and, combined with the chiral asymmetry, it could be the platform for a new generation of reconfigurable devices for THz wave polarization manipulation.