[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Active Metasurface Devices for Terahertz Wave Front Modulation

摘要： Terahertz (THz) radiation, which is sandwiched between the infrared and microwave in the electromagnetic spectrum, has become more and more attractive due to its special properties. Compared with the quick development of THz sources and detectors, THz functional devices are lagging behind, especially the devices for wave front modulation. Metasurface, a kind of artificial materials, is enable effective manipulation of the amplitude, phase and polarization state of electromagnetic waves with subwavelength spatial resolution. It has been used for ultrathin planar lenses, complex light field generation, spin orbital angular momentum coupling, and metasurface holograms. However, the function of this kind of metasurface based devices are fixed once they are fabricated, the spatial THz modulation which can dynamically modulate the wave front of THz radiation is demand in high resolution THz imaging and THz communication. In this presentation, we present a novel approach for generating arbitrary wave fronts of a THz beam by dynamically creating metasurface structures through illuminating a super thin silicon wafer with femtosecond laser, which is spatially modulated to result in an array of reconfigurable subwavelength resonators. The wave front of the THz beam is then determined by forming spatial profiles of the Pancharatnam-Berry scattering phase by dynamically controlling the resonator orientation. Proof-of-concept experiments demonstrate that streaming holographic images and lenses of variable focal length can be realized in real time. The theoretical expectations and experimental results are shown in Fig. 1, the generated patterns are matching with the theoretical exceptions. The reconfigurable scheme demonstrated here is convenient and fast, and may lead to advances in a host of THz applications.