4th Physics Institute and Research Center SCOPE, University of Stuttgart , D-70569 Stuttgart, Germany.
ACS Nano. 2014 Oct 28;8(10):10885-92. doi: 10.1021/nn504708t. Epub 2014 Oct 6.
Plasmonic devices with absorbance close to unity have emerged as essential building blocks for a multitude of technological applications ranging from trace gas detection to infrared imaging. A crucial requirement for such elements is the angle independence of the absorptive performance. In this work, we develop theoretically and verify experimentally a quantitative model for the angular behavior of plasmonic perfect absorber structures based on an optical impedance matching picture. To achieve this, we utilize a simple and elegant k-space measurement technique to record quantitative angle-resolved reflectance measurements on various perfect absorber structures. Particularly, this method allows quantitative reflectance measurements on samples where only small areas have been nanostructured, for example, by electron-beam lithography. Combining these results with extensive numerical modeling, we find that matching of both the real and imaginary parts of the optical impedance is crucial to obtain perfect absorption over a large angular range. Furthermore, we successfully apply our model to the angular dispersion of perfect absorber geometries with disordered plasmonic elements as a favorable alternative to current array-based designs.
等离子体器件的吸收率接近 1 已成为多种技术应用的基本组成部分，从痕量气体检测到红外成像。对于这些元件，一个关键的要求是吸收性能的角度独立性。在这项工作中，我们从光学阻抗匹配的角度出发，理论上提出并实验验证了一种用于等离子体完美吸收器结构角度行为的定量模型。为此，我们利用一种简单而优雅的 k 空间测量技术，对各种完美吸收器结构进行了定量的角度分辨反射率测量。特别地，这种方法允许对仅纳米结构化的小面积样品进行定量反射率测量，例如通过电子束光刻。将这些结果与广泛的数值建模相结合，我们发现光学阻抗的实部和虚部的匹配对于在大角度范围内获得完美吸收是至关重要的。此外，我们成功地将我们的模型应用于具有无序等离子体元件的完美吸收器几何形状的角度色散，这是对当前基于阵列设计的有利替代方案。
