Interaction of Ultrashort-Laser Pulses with Induced Undercritical Plasmas in Fused Silica
Interaction of Ultrashort-Laser Pulses with Induced Undercritical Plasmas in Fused Silica
复制标题
超短激光脉冲与熔融石英中感应亚临界等离子体的相互作用
DOI：
10.1103/physreva.85.013808
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发表时间：
2012
影响因子：
2.9
通讯作者：
R. Stoian
中科院分区：
文献类型：
--
作者：
J. Gulley;S. Winkler;W. Dennis;C. Liebig;R. Stoian
在损伤阈值附近的超快光-材料相互作用通常是通过损伤介质材料的事后分析来研究的。相应的超短脉冲在材料中传播的模拟经常被用来获得导致这种损伤的过程的额外见解。然而，这种实验和数值结果之间的比较往往是定性的，接近但不超过损伤阈值的脉冲不会对材料造成永久性的变化，从而无法进行死后分析。在本文中，提出了一系列的实验，测量了140-fs激光脉冲通过熔融石英样品后的近场和远场特性，其中产生了非临界电子等离子体。同时，给出了根据近场光束轮廓和频率分辨光门（FROG）迹线对激光脉冲进行数值构造的仿真结果。研究发现，为了对这些数据进行定量比较，模拟中应放弃激光脉冲的圆柱对称，而采用完全的3 + 1D笛卡尔表示。进一步比较实验和计算损伤阈值表明，Drude模型预测的时间校正效应在脉冲演化和等离子体形成的物理过程中都起着至关重要的作用。在远场测量中产生的脉冲时空依赖性的影响导致无法恢复的FROG痕迹。然而，通过仿真和实验表明，在测量时间脉冲幅度时，使用适当的光束孔径可以消除这种影响。
Ultrafast light-material interactions near the damage threshold are often studied using postmortem analysis of damaged dielectric materials. Corresponding simulations of ultrashort pulse propagation through the material are frequently used to gain additional insight into the processes leading to such damage. However, comparison between such experimental and numerical results is often qualitative, and pulses near to but not exceeding the damage threshold leave no permanent changes in the material for postmortem analysis. In this article, a series of experiments is presented that measures the near- and far-field properties of a 140-fs laser pulse after propagation through a fused silica sample in which a noncritical electron plasma was generated. Concurrently, results from simulations in which the laser pulse was numerically constructed according to the nearfield beam profile and frequency resolved optical gating (FROG) trace are presented. It is found that to extract a quantitative comparison of such data, cylindrical symmetry of the laser pulse in simulations should be abandoned in favor of a fully 3 + 1D Cartesian representation. Further comparison of experimental and calculated damage thresholds shows that time-corrective effects predicted by the Drude model play a critical role in the physics of both pulse evolution and plasma formation. The influence of resulting spatiotemporal dependences of the pulse in far-field measurements leads to unretrievable FROG traces. However, it is shown through both simulation and experiment that the use of an appropriate beam aperture will eliminate this effect when measuring the temporal pulse amplitude.