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 encounte...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.展开更多
Metasurfaces incorporating graphene hold great promise for the active manipulation of terahertz waves. However,it remains challenging to design a broadband graphene-based terahertz metasurface with switchable function...Metasurfaces incorporating graphene hold great promise for the active manipulation of terahertz waves. However,it remains challenging to design a broadband graphene-based terahertz metasurface with switchable functionality of half-wave plate(HWP) and quarter-wave plate(QWP). Here, we propose a graphene–metal hybrid metasurface for achieving broadband switchable HWP/QWP in the terahertz regime. Simulation results show that, by varying the Fermi energy of graphene from 0 eV to 1 eV, the function of the reflective metasurface can be switched from an HWP with polarization conversion ratio exceeding 97% over a wide band ranging from 0.7 THz to 1.3 THz, to a QWP with ellipticity above 0.92over 0.78 THz–1.33 THz. The sharing bandwidth reaches up to 0.52 THz and the relative bandwidth is as high as 50%.We expect this broadband and dynamically switchable terahertz HWP/QWP will find applications in terahertz sensing,imaging, and telecommunications.展开更多
基金This work was sponsored by the 973 programs(Nos.2011CBA00200 and 2012CB921803)the National Natural Science Foundation of China(Nos.61490714,11304151 and 61435008)+5 种基金the PhD Programs Foundation of the Ministry of Education of China(No.20120091120020)Yan-Qing Lu appreciates the support from National Science Fund for Distinguished Young Scholars(No.61225026)the Program for Changjiang Scholars and Innovative Research Team in University(No.IRT13021)Biao-Bing Jin appreciates the support from the 973 program(No.2014CB339800)the National Natural Science Foundation of China(Nos.61371035 and 11227904)Cooperative Innovation Centre of Terahertz Science,University of Electronic Science and Technology(Chengdu,China).
文摘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.
基金supported by Shenzhen Research Foundation (Grant No. JCYJ20180507182444250)。
文摘Metasurfaces incorporating graphene hold great promise for the active manipulation of terahertz waves. However,it remains challenging to design a broadband graphene-based terahertz metasurface with switchable functionality of half-wave plate(HWP) and quarter-wave plate(QWP). Here, we propose a graphene–metal hybrid metasurface for achieving broadband switchable HWP/QWP in the terahertz regime. Simulation results show that, by varying the Fermi energy of graphene from 0 eV to 1 eV, the function of the reflective metasurface can be switched from an HWP with polarization conversion ratio exceeding 97% over a wide band ranging from 0.7 THz to 1.3 THz, to a QWP with ellipticity above 0.92over 0.78 THz–1.33 THz. The sharing bandwidth reaches up to 0.52 THz and the relative bandwidth is as high as 50%.We expect this broadband and dynamically switchable terahertz HWP/QWP will find applications in terahertz sensing,imaging, and telecommunications.
基金supported by the Natural Science Foundation of Xinjiang (2023D01E17)the National Natural Science Foundation of China (22335007)+2 种基金Tianshan Talents-Young Science and Technology Top Talents Project (2022TSYCCX0078 and 2022TSYCTD0005)Xinjiang Major Science and Technology Project (2021A01001 and2022A01005-5)the Key Research Program of Frontier Sciences,CAS(ZDBS-LY-SLH035)。
