Tuesday, July 4, 2017
Abstract-Strong broadband terahertz optical activity through control of the Blaschke phase with chiral metasurfaces
Michael A. Cole, Wen-chen Chen, Mingkai Liu, Sergey S. Kruk, Willie J. Padilla, Ilya V. Shadrivov, David A. Powell
We demonstrate terahertz chiral metamaterials that achieve resonant transmission and strong optical activity. This response is realized in a metasurface coupled to its Babinet complement, with additional twist. Uniquely, the optical activity achieved in this type of metamaterial is weakly dispersive around the resonant transmission maxima, but can be highly dispersive around the transmission minima. It has recently been shown that this unique optical activity response is closely related to zeros in the transmission spectra of circular polarizations through the Kramers-Kronig relations and strong resonant features in the optical activity spectrum corresponding to the Blaschke phase terms. Here we demonstrate how modifying the meta-atom geometry greatly affects the location and magnitude of these Blaschke phase terms. We study three different meta-atoms, which are variations on the simple cross structure. Their responses are measured using terahertz time-domain spectroscopy, and analyzed via numerical simulations.