Understanding how light interacts with matter at the nanoscale is pivotal if one is to properly engineer nano-antennas, filters and other devices whose geometrical features approach atomic size. We report experimental results on second and third harmonic generation from 20 nm- and 70 nm-thick gold layers, for TE- and TM-polarized incident light pulses. We discuss the relative roles that bound electrons and an intensity dependent free electron density (hot electrons) play in third harmonic generation. While planar structures are generally the simplest to fabricate, metal layers that are only a few nanometers thick and partially transparent are almost never studied. Yet, transmission offers an additional reference point to compare experimental measurements with theoretical models. Our experimental results are explained well within the context of the microscopic hydrodynamic model that we employ to simulate second and third harmonic conversion efficiencies. Using our experimental observations we estimate $\mid \chi ^{(3)}_{1064nm}\mid \approx 10^{-18}$ $(\textrm{m/V})^2$, triggered mostly by hot electrons.

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金纳米层的谐波产生：结合和热电子对非线性色散的贡献

如果要正确设计纳米天线，滤波器和其他几何特征接近原子尺寸的设备，了解光在纳米尺度上如何与物质相互作用至关重要。我们报告了从20 nm和70 nm厚的金层产生二次谐波和三次谐波的实验结果，用于TE和TM偏振入射光脉冲。我们讨论了束缚电子和强度相关的自由电子密度（热电子）在三次谐波产生中的相对作用。虽然平面结构通常最容易制造，但几乎从未研究过只有几纳米厚且部分透明的金属层。然而，传输提供了一个额外的参考点，可以将实验测量结果与理论模型进行比较。我们的实验结果在微观流体力学模型的背景下得到了很好的解释，该模型用于模拟二次谐波和三次谐波的转换效率。使用我们的实验观察，我们可以估算$ \ mid \ chi ^ {（3）} _ {1064nm} \ mid \ approx 10 ^ {-18} $ $（\ textrm {m / V}）^ 2 $，主要是由热电子触发的。