Institute of Technology and Innovation (ITI), University of Southern Denmark, Niels Bohrs Allé 1, DK-5230 Odense M, Denmark.
Nano Lett. 2013 Feb 13;13(2):829-34. doi: 10.1021/nl304761m. Epub 2013 Jan 27.
We demonstrate that metal-insulator-metal configurations, with the top metal layer consisting of a periodic arrangement of differently sized nanobricks, can be designed to function as broadband focusing flat mirrors. Using 50-nm-high gold nanobricks arranged in a 240-nm-period lattice on the top of a 50-nm-thick layer of silicon dioxide deposited on a continuous 100-nm-thick gold film, we realize a 17.3 × 17.3 μm(2) flat mirror that efficiently reflects (experiment: 14-27%; theory: 50-78%) and focuses a linearly polarized (along the direction of nanobrick size variation) incident beam in the plane of its polarization with the focal length, which changes from ~15 to 11 μm when tuning the light wavelength from 750 to 950 nm, respectively. Our approach can easily be extended to realize the radiation focusing in two dimensions as well as other optical functionalities by suitably controlling the phase distribution of reflected light.
我们证明，由不同大小纳米砖周期性排列组成的顶金属层的金属-绝缘体-金属结构，可以设计成宽带聚焦平面反射镜。我们在沉积在连续的 100nm 厚金膜上的 50nm 厚二氧化硅层的顶部，使用高度为 50nm 的金纳米砖，以 240nm 的周期晶格排列，实现了一个 17.3μm×17.3μm（2）的平面反射镜，它可以有效地反射（实验：14-27%；理论：50-78%）和聚焦线性偏振（沿纳米砖尺寸变化方向）入射光束，其焦距从 750nm 到 950nm 的波长调谐时，分别从约 15μm 变化到 11μm。通过适当控制反射光的相位分布，我们的方法可以很容易地扩展到实现二维辐射聚焦和其他光学功能。
