Metasurfaces have become a new photonic structure for providing potential applications to develop integrated devices with small thickness, because they can introduce an abrupt phase change by arrays of scatterers. To ...Metasurfaces have become a new photonic structure for providing potential applications to develop integrated devices with small thickness, because they can introduce an abrupt phase change by arrays of scatterers. To be applied more widely, active metasurface devices are highly desired. Here, a tunable terahertz meta-lens whose focal length is able to be electrically tuned by ～4.45λ is demonstrated experimentally. The lens consists of a metallic metasurface and a monolayer graphene. Due to the dependence of the abrupt phase change of the metasurface on the graphene chemical potential, which can be modulated using an applied gate voltage, the focal length is changed from 10.46 to 12.24 mm when the gate voltage increases from 0 to 2.0 V. Experimental results are in good agreement with the theoretical hypothesis. This type of electrically controlled meta-lens could widen the application of terahertz technology.展开更多
The unrestricted control of circularly polarized(CP)terahertz(THz)waves is important in science and applications,but conventional THz devices suffer from issues of bulky size and low efficiency.Although Pancharatnam-B...The unrestricted control of circularly polarized(CP)terahertz(THz)waves is important in science and applications,but conventional THz devices suffer from issues of bulky size and low efficiency.Although Pancharatnam-Berry(PB)metasurfaces have shown strong capabilities to control CP waves,transmission-mode PB devices realized in the THz regime are less efficient,limiting their applications in practice.Here,based on Jones matrix analysis,we design a trilayer structure(thickness of ~λ/5)and experimentally demonstrate that the structure can serve as a highly efficient transmissive meta-atom(relative efficiency of ~90%)to build PB metadevices for manipulating CP THz waves.Two ultrathin THz metadevices are fabricated and experimentally characterized with a z-scan THz imaging system.The first device can realize a photonic spin Hall effect with an experimentally demonstrated relative efficiency of ~90%,whereas the second device can generate a high-quality background-free CP Bessel beam with measured longitudinal and transverse field patterns that exhibit the nondiffracting characteristics of a Bessel beam.All the experimental results are in excellent agreement with full-wave simulations.Our results pave the way to freely manipulate CP THz beams,laying a solid basis for future applications such as biomolecular control and THz signal transportation.展开更多
基金National Key R&D Program of China(2017YFB1002900)973 Program of China(2013CBA01702)+1 种基金National Natural Science Foundation of China(NSFC)(11404224,1174243,11774246,61405012,61420106014)Excellent Young Scholars Research Fund of Beijing Institute of Technology(BIT)
文摘Metasurfaces have become a new photonic structure for providing potential applications to develop integrated devices with small thickness, because they can introduce an abrupt phase change by arrays of scatterers. To be applied more widely, active metasurface devices are highly desired. Here, a tunable terahertz meta-lens whose focal length is able to be electrically tuned by ～4.45λ is demonstrated experimentally. The lens consists of a metallic metasurface and a monolayer graphene. Due to the dependence of the abrupt phase change of the metasurface on the graphene chemical potential, which can be modulated using an applied gate voltage, the focal length is changed from 10.46 to 12.24 mm when the gate voltage increases from 0 to 2.0 V. Experimental results are in good agreement with the theoretical hypothesis. This type of electrically controlled meta-lens could widen the application of terahertz technology.
基金funded by the National Key Research and Development Program of China(no.2017YFA0700201 and no.2017YFA0303504)National Natural Science Foundation of China(no.11734007,no.11474057,no.11674068,no.11474206,no.11774246,no.91850101,and no.11874118)Natural Science Foundation of Shanghai(no.16ZR1445200,no.16JC1403100,and no.18ZR1403400).
文摘The unrestricted control of circularly polarized(CP)terahertz(THz)waves is important in science and applications,but conventional THz devices suffer from issues of bulky size and low efficiency.Although Pancharatnam-Berry(PB)metasurfaces have shown strong capabilities to control CP waves,transmission-mode PB devices realized in the THz regime are less efficient,limiting their applications in practice.Here,based on Jones matrix analysis,we design a trilayer structure(thickness of ~λ/5)and experimentally demonstrate that the structure can serve as a highly efficient transmissive meta-atom(relative efficiency of ~90%)to build PB metadevices for manipulating CP THz waves.Two ultrathin THz metadevices are fabricated and experimentally characterized with a z-scan THz imaging system.The first device can realize a photonic spin Hall effect with an experimentally demonstrated relative efficiency of ~90%,whereas the second device can generate a high-quality background-free CP Bessel beam with measured longitudinal and transverse field patterns that exhibit the nondiffracting characteristics of a Bessel beam.All the experimental results are in excellent agreement with full-wave simulations.Our results pave the way to freely manipulate CP THz beams,laying a solid basis for future applications such as biomolecular control and THz signal transportation.
