Nanostructured gold films as broadband terahertz antireflection coatings

被引:150
|
作者
Thoman, Andreas [1 ]
Kern, Andreas [1 ]
Helm, Hanspeter [1 ]
Walther, Markus [1 ]
机构
[1] Univ Freiburg, Freiburg Mat Res Ctr, D-79104 Freiburg, Germany
来源
PHYSICAL REVIEW B | 2008年 / 77卷 / 19期
关键词
D O I
10.1103/PhysRevB.77.195405
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
The potential of nanometer-thick, randomly nanostructured gold films as broadband wave impedance-matching coatings for nondispersive substrates in the terahertz frequency range is demonstrated. Based on a wave impedance approach and the specific non-Drude conductivity of our films, we model the reflectivity at the coated inter-face between silicon and air and show that nanostructured films offer a considerably better broadband performance than conventional bulk metallic layers. The predictions from the theoretical model are verified in experimental studies of different gold nanostructures investigated by terahertz time-domain spectroscopy in the frequency range of 0.2-2.2 THz. An extension of a previously developed subgridding scheme for the finite-difference time-domain method allows us to simulate terahertz-pulse propagation through uncoated and coated samples and to follow attenuation and reshaping of the internally reflected pulse when the film thickness is varied with subnanometer precision.
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页数:9
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