Zhang Yong, Zhou Lin, Li Jia-qi, Wang Qian-jin, Huang Cheng-ping
Department of Applied Physics, Nanjing Tech University, Nanjing 210009, P.R. China.
National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, P. R. China.
Sci Rep. 2015 May 14;5:10119. doi: 10.1038/srep10119.
Enhanced high-order diffractions which are spatially dispersive are desirable in such as spectroscopy studies, thin-film solar cells, etc. Conventionally, the dielectric gratings can be used to realize the enhanced diffraction, but the facets are usually rugged and optically thick (~μm). Plasmonic materials may exhibit unprecedented ability for manipulating light. Nonetheless, much interest has been focused on the subwavelength metasurfaces working in the zero-order regime. Here, we show that ultra-broadband and strongly enhanced diffraction can be achieved with the super-wavelength metasurfaces. For the purpose, we employ symmetric or asymmetric metal patches on a ground metal plane, which support the localized oscillation of free electrons and enhanced scattering of light. The zero-order reflection is suppressed, giving rise to an enhancement of first-order diffraction (50 ~ 95%) in an ultra-wide bandwidth (600 ~ 1500 nm). The proposed plasmonic structure is planar and ultra-thin (with an etching depth of only 80 nm), showing new potential for constructing compact and efficient dispersive elements.
在诸如光谱学研究、薄膜太阳能电池等领域，空间色散的增强高阶衍射是很有必要的。传统上，介质光栅可用于实现增强衍射，但其刻面通常粗糙且光学厚度较大（约为微米级）。等离子体材料可能展现出前所未有的光操控能力。尽管如此，许多研究兴趣都集中在零阶模式下工作的亚波长超表面上。在此，我们表明超波长超表面能够实现超宽带且强烈增强的衍射。为此，我们在接地金属平面上采用对称或不对称的金属贴片，这些贴片支持自由电子的局部振荡并增强光的散射。零阶反射被抑制，从而在超宽带（600～1500纳米）内实现一阶衍射增强（50%～95%）。所提出的等离子体结构是平面且超薄的（蚀刻深度仅为80纳米），这为构建紧凑高效的色散元件展现了新的潜力。
