Broadband tunable liquid crystal terahertz waveplates driven with porous graphene electrodes

• DOI: 10.1038/lsa.2015.26
• Publication Date: 2015-02-27T07:22:08Z
• Authors: Lei Wang; Xiao-Wen Lin; Wei Hu; Guang-Hao Shao; Peng Chen; Lan-Ju Liang; Biao-Bing Jin; Pei-Heng Wu; Hao Qian; Yi-Nong Lu; Xiao Liang; Zhi-Gang Zheng; Yan-Qing Lu
• Keywords: 02 engineering and technology; 0210 nano-technology; 7. Clean energy

AbstractVersatile 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.