School of Engineering and Applied Sciences, Harvard University , Cambridge, Massachusetts 02138, United States.
Nano Lett. 2014 Nov 12;14(11):6526-32. doi: 10.1021/nl503104n. Epub 2014 Oct 20.
Dynamically reconfigurable metasurfaces open up unprecedented opportunities in applications such as high capacity communications, dynamic beam shaping, hyperspectral imaging, and adaptive optics. The realization of high performance metasurface-based devices remains a great challenge due to very limited tuning ranges and modulation depths. Here we show that a widely tunable metasurface composed of optical antennas on graphene can be incorporated into a subwavelength-thick optical cavity to create an electrically tunable perfect absorber. By switching the absorber in and out of the critical coupling condition via the gate voltage applied on graphene, a modulation depth of up to 100% can be achieved. In particular, we demonstrated ultrathin (thickness < λ0/10) high speed (up to 20 GHz) optical modulators over a broad wavelength range (5-7 μm). The operating wavelength can be scaled from the near-infrared to the terahertz by simply tailoring the metasurface and cavity dimensions.
动态可重构超表面在大容量通信、动态波束成形、高光谱成像和自适应光学等应用中开辟了前所未有的机遇。由于调谐范围和调制深度非常有限，高性能基于超表面的器件的实现仍然是一个巨大的挑战。在这里，我们展示了一种由石墨烯上的光学天线组成的广泛可调谐超表面，可以集成到亚波长厚的光学腔中，以创建电可调谐的完美吸收器。通过在石墨烯上施加栅极电压，将吸收器切换到和离开临界耦合条件，可以实现高达 100%的调制深度。特别是，我们演示了在很宽的波长范围内（5-7 μm）具有超轻薄（厚度<λ0/10）、高速（高达 20 GHz）的光学调制器。通过简单地调整超表面和腔的尺寸，可以将工作波长从近红外扩展到太赫兹。
