arXiv 1807.077722018-07-20physics.plasm-ph

固体对高强度、高对比度飞秒Laser脉冲的吸收

Absorption of High Intensity, High Contrast Femtosecond Laser Pulses by a Solid

Amitava Adak, Amit D. Lad, Moniruzzaman Shaikh, Indranuj Dey, Deep Sarkar, G. Ravindra Kumar

备注：: 5 pages, 6 figures

摘要：

对固体中高强度飞秒激光吸收的基本理解对于高能量密度科学至关重要。这个多维问题有许多变量，如激光参数，固体靶材料和几何形状的激励。这对于基本了解强激光-物质相互作用以及“等离子体镜”等应用都很重要。在这里，我们实验观察到高强度，高对比度飞秒激光吸收的光学抛光熔融石英靶在近相对论激光强度（$\sim$ 10 $^{18}$ W/cm $^2$）。作为入射角和入射能量的函数的激光吸收研究为$p$和$s$偏振脉冲的详细信息，提供了一个强有力的指示存在的碰撞过程。在最佳入射角下，几乎高达80%的激光（$p$偏振）能量被吸收在靶中。在近相对论强度下如此高的吸收百分比以前从未观察到。在较小的入射角下，高反射率（例如，在30 $^\circ$入射下约60 - 70%）表明，该研究基本上与近相对论强度下的等离子体镜相关。

英文摘要：

The basic understanding of high-intensity femtosecond laser absorption in a solid is crucial for high-energy-density science. This multidimensional problem has many variables like laser parameters, solid target material, and geometry of the excitation. This is important for a basic understanding of intense laser-matter interaction as well for applications such as `plasma mirror'. Here, we have experimentally observed high-intensity, high-contrast femtosecond laser absorption by an optically polished fused silica target at near-relativistic laser intensities ($\sim$10$^{18}$ W/cm$^2$). The laser absorption as a function of angle of incidence and incident energy is investigated for both $p$- and $s$-polarized pulses in detail, providing a strong indication of the presence of collisionless processes. At an optimum angle of incidence, almost as large as 80% of the laser ($p$-polarized) energy gets absorbed in the target. Such a high percentage of absorption at near-relativistic intensities has not been observed before. At smaller angles of incidence the high reflectivity (e.g. about 60 - 70% at 30$^\circ$ incidence) indicate that, this study is fundamentally relevant for plasma mirrors at near-relativistic intensities.

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