Finke O, Vábek J, Nevrkla M, Bobrova N, Hort O, Jurkovičová L, Albrecht M, Jančárek A, Catoire F, Skupin S, Nejdl J
ELI Beamlines Centre, FZU-Institute of Physics of the Czech Academy of Sciences, Na Slovance 2, 182 21, Prague, Czechia.
Czech Technical University in Prague, FNSPE, Břehová 7, 115 19, Prague 1, Czechia.
Sci Rep. 2022 May 11;12(1):7715. doi: 10.1038/s41598-022-11313-6.
One of the main difficulties of efficiently generating high-order harmonics in long neutral-gas targets is to reach the phase-matching conditions. The issue is that the medium cannot be sufficiently ionized by the driving laser due to plasma defocusing. We propose a method to improve the phase-matching by pre-ionizing the gas using a weak capillary discharge. We have demonstrated this mechanism, for the first time, in absorption-limited XUV generation by an 800 nm femtosecond laser in argon and krypton. The ability to control phase-mismatch is confirmed by an analytical model and numerical simulations of the entire generation process. Our method allows to increase the efficiency of the harmonic generation significantly, paving the way towards photon-hungry applications of these compact short-wavelength sources.
在长中性气体靶中高效产生高次谐波的主要困难之一是达到相位匹配条件。问题在于由于等离子体散焦，驱动激光无法使介质充分电离。我们提出一种通过使用弱毛细管放电对气体进行预电离来改善相位匹配的方法。我们首次在氩气和氪气中用800纳米飞秒激光产生吸收受限的极紫外光过程中演示了这种机制。通过对整个产生过程的解析模型和数值模拟证实了控制相位失配的能力。我们的方法能够显著提高谐波产生的效率，为这些紧凑的短波长光源在急需光子的应用方面铺平了道路。
