Metasurface holograms reaching 80% efficiency
Metasurface holograms reaching 80% efficiency
复制标题
DOI：
10.1038/nnano.2015.2
复制
发表时间：
2015-04-01
影响因子：
38.3
通讯作者：
Zhang, Shuang
中科院分区：
文献类型：
--
作者：
Zheng, Guoxing;Muehlenbernd, Holger;Zhang, Shuang
由超薄等离子体结构覆盖的表面--所谓的亚表面(1-4)--最近被证明能够完全控制光的相位，代表了创新光学元件设计的新范例，例如超薄平板透镜(5-7)、用于表面等离子体激元的定向耦合器(4，8-10)和波片涡旋光束产生(1，11)。在各种亚表面中，几何亚表面由一系列具有不同取向的等离子体纳米棒组成，由于其相分布的几何性质而显示出优越的相控制(12，13)。超表面最近被用来制作计算机生成的全息图(14-19)，但在可见光波长下的全息图效率仍然太低，不能用于实际目的。本文报道了一种在825 nm处获得80%衍射效率、带宽在630 nm到1050 nm之间的几何亚表面全息图的设计和实现。本文展示的16能级位相计算全息图结合了几何变形表面和反射光的优点，前者可以更好地控制位相轮廓，后者可以实现高的偏振转换效率。具体地说，全息图的设计将磨碎的金属平面与几何亚表面相结合，从而提高了两个圆偏振态之间的转换效率，从而在不使制造过程复杂化的情况下获得高的衍射效率。由于这些优势，我们的策略可能适用于各种实际的全息应用。
Surfaces covered by ultrathin plasmonic structures so-called metasurfaces(1-4)-have recently been shown to be capable of completely controlling the phase of light, representing a new paradigm for the design of innovative optical elements such as ultrathin flat lenses(5-7), directional couplers for surface plasmon polaritons(4,8-10) and wave plate vortex beam generation(1,11). Among the various types of metasurfaces, geometric metasurfaces, which consist of an array of plasmonic nanorods with spatially varying orientations, have shown superior phase control due to the geometric nature of their phase profile(12,13). Metasurfaces have recently been used to make computer-generated holograms(14-19), but the hologram efficiency remained too low at visible wavelengths for practical purposes. Here, we report the design and realization of a geometric metasurface hologram reaching diffraction efficiencies of 80% at 825 nm and a broad bandwidth between 630 nm and 1,050 nm. The 16-level-phase computer-generated hologram demonstrated here combines the advantages of a geometric metasurface for the superior control of the phase profile and of reflectarrays for achieving high polarization conversion efficiency. Specifically, the design of the hologram integrates a ground metal plane with a geometric metasurface that enhances the conversion efficiency between the two circular polarization states, leading to high diffraction efficiency without complicating the fabrication process. Because of these advantages, our strategy could be viable for various practical holographic applications.