Saturday, February 28, 2015
Abstract-Broadband tunable liquid crystal terahertz waveplates driven with porous graphene electrodes
Lei Wang1,*, Xiao-Wen Lin1,*, Wei Hu1, Guang-Hao Shao1, Peng Chen1, Lan-Ju Liang2, Biao-Bing Jin2, Pei-Heng Wu2, Hao Qian3, Yi-Nong Lu3, Xiao Liang4, Zhi-Gang
Zheng1 and Yan-Qing Lu1
Versatile devices, especially tunable ones, for terahertz imaging, sensing and high-speed communication, are in high demand. Liquid crystal based components are perfect candidates in the optical range; however, they encounter significant challenges in the terahertz band, particularly the lack of highly transparent electrodes and the drawbacks induced by a thick cell. Here, a strategy to overcome all these challenges is proposed: Few-layer porous graphene is employed as an electrode with a transmittance of more than 98%. A subwavelength metal wire grid is utilized as an integrated high-efficiency electrode and polarizer. The homogeneous alignment of a high-birefringence liquid crystal is implemented on both frail electrodes via a non-contact photo-alignment technique. A tunable terahertz waveplate is thus obtained. Its polarization evolution is directly demonstrated. Furthermore, quarter-wave plates that are electrically controllable over the entire testing range are achieved by stacking two cells. The proposed solution may pave a simple and bright road toward the development of various liquid crystal terahertz apparatuses.