Wöstmann Michael, Splitthoff Lukas, Zacharias Helmut
Opt Express. 2018 May 28;26(11):14524-14537. doi: 10.1364/OE.26.014524.
High-harmonic generation is widely used for providing extreme ultraviolet radiation in attosecond science. Such experiments include photoelectron spectroscopy, diffractive imaging, or the investigation of spin dynamics. Many applications are restricted by a low photon flux which originates from the low efficiency of the generation process. In this article an effective method based on the quasi-phase-matched generation of high harmonics in spatially structured, laser ablated plasma is demonstrated. Through a proper dimensioning of the plasma structure, the harmonic yield is optimized for a controllable range of harmonic orders. By using four coherent zones, the intensity of a single harmonic is increased to a maximal possible value of 16 compared to using a single zone. The Gouy phase shift of the fundamental field is identified as the primary effect responsible for constructive interference of the harmonic fields generated in the individual plasma jets of the plasma structure.
高次谐波产生在阿秒科学中被广泛用于提供极紫外辐射。此类实验包括光电子能谱、衍射成像或自旋动力学研究。许多应用受到光子通量低的限制，这源于产生过程的低效率。本文展示了一种基于在空间结构化、激光烧蚀等离子体中准相位匹配产生高次谐波的有效方法。通过对等离子体结构进行适当的尺寸设计，谐波产率在可控的谐波阶数范围内得到优化。与使用单个区域相比，通过使用四个相干区域，单个谐波的强度增加到最大可能值16。基波场的古依相移被确定为对等离子体结构中各个等离子体射流产生的谐波场的相长干涉起主要作用的效应。
