We demonstrate an interesting modulation of fast electron temperature and yield as a function of the thickness of nanocrystalline coating on a dielectric target, in femtosecond, intense laser interaction with a solid target. We measure the fast electron energy spectrum for fused silica targets coated with ultrathin, nanocrystalline Cu films with thickness ranging from 30 to 100 nm and compare them with those from a planar, uncoated polished silica surface. The fast electron temperature exhibits an unexpected dependence on the film thickness, peaking at 30 and 45 nm and falling off for films with higher thicknesses. During these experiments, the size of the Cu nanograins was kept constant and only the film thickness was varied. We find that—in the low thickness limit—the target thickness acts as an additional length scale, independent of the surface topography, and needs to be separately optimized for maximizing the generation of fast electrons from high-intensity, ultrashort laser–matter interaction.

中文翻译：

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强、超短激光-固体相互作用中快速电子特性对纳米晶薄膜靶厚度的依赖性

我们展示了快速电子温度和产量的有趣调制，作为介电目标上纳米晶涂层厚度的函数，在飞秒内，强激光与固体目标相互作用。我们测量了涂覆有厚度为 30 到 100 nm 的超薄纳米晶铜膜的熔融石英靶的快速电子能谱，并将它们与平面、未涂覆的抛光石英表面的那些进行比较。快速电子温度表现出对薄膜厚度的出乎意料的依赖性，在 30 和 45 nm 处达到峰值，对于具有更高厚度的薄膜而下降。在这些实验中，Cu 纳米颗粒的尺寸保持不变，只有薄膜厚度发生变化。我们发现——在低厚度极限——目标厚度作为一个额外的长度尺度，