Broadband tunable liquid crystal terahertz waveplates driven with porous graphene electrodes, Light Sci. Appl., 4, e253 (2015)
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.