Department of Physics, The Blackett Laboratory, Imperial College London, London SW7 2AZ, UK.
1] INPAC, K. U. Leuven Celestijnenlaan 200 D, Leuven B-3001, Belgium [2] IMEC, Kapeldreef 75, Leuven 3001, Belgium.
Nat Commun. 2014 Apr 30;5:3748. doi: 10.1038/ncomms4748.
Optical antennas transform light from freely propagating waves into highly localized excitations that interact strongly with matter. Unlike their radio frequency counterparts, optical antennas are nanoscopic and high frequency, making amplitude and phase measurements challenging and leaving some information hidden. Here we report a novel spectral interferometric microscopy technique to expose the amplitude and phase response of individual optical antennas across an octave of the visible to near-infrared spectrum. Although it is a far-field technique, we show that knowledge of the extinction phase allows quantitative estimation of nanoantenna absorption, which is a near-field quantity. To verify our method we characterize gold ring-disk dimers exhibiting Fano interference. Our results reveal that Fano interference only cancels a bright mode's scattering, leaving residual extinction dominated by absorption. Spectral interference microscopy has the potential for real-time and single-shot phase and amplitude investigations of isolated quantum and classical antennas with applications across the physical and life sciences.
光学天线将自由传播的光波转换为高度局域化的激发，与物质强烈相互作用。与射频天线不同，光学天线是纳米级的高频天线，这使得幅度和相位的测量具有挑战性，并隐藏了一些信息。在这里，我们报告了一种新的光谱干涉显微镜技术，可以在可见到近红外光谱的一个倍频程范围内揭示单个光学天线的幅度和相位响应。尽管这是一种远场技术，但我们表明，消光相位的知识允许对纳米天线的吸收进行定量估计，这是一种近场量。为了验证我们的方法，我们对表现出 Fano 干涉的金环盘二聚体进行了表征。我们的结果表明，Fano 干涉仅抵消了一个亮模的散射，而残留的消光主要由吸收主导。光谱干涉显微镜具有实时和单次相位和幅度研究孤立量子和经典天线的潜力，在物理和生命科学中有广泛的应用。
