Intense XUV sub-fs pulses using extreme soliton dynamics in hollow-core fibers

产生明亮的阿秒长的XUV脉冲对于各种应用具有内在的重要性。目前，唯一的方法是采用高次谐波产生(HHG)，但其转换效率相当低。这里，提出了另一种方法，根据初步模拟，允许在波长降至50 nm时对持续时间短于500的脉冲的高达5%的转换效率。该方法基于光学克尔效应，利用了现代充氦空芯“Kagome”光纤中短周期强脉冲的动力学特性。从孤子在光纤中传输产生新的频率是众所周知的，但这里通过使用a)极短的输入脉冲和b)可能的最高强度来利用一种根本的新制度。经过几厘米的传播后，这种脉冲将在XUV范围内发出共振辐射。XUV脉冲的啁啾可以通过在预电离气体中的线性传输来补偿。成功的关键是准备几个周期的大约短脉冲。5ps的持续时间和约20微焦耳的能量，这将通过自制的OPCPA设置来实现。

Generation of bright attosecond-long XUV pulses is of immanent importance for various applications. Currently, the only way is to employ high harmonic generation (HHG), which suffers from rather low conversion efficiencies. Here, an alternative approach is proposed, allowing, according to preliminary simulations, for up to 5 % conversion efficiency to pulses with durations shorter than 500 as at wavelengths down to 50 nm. The method is based on the optical Kerr effect and exploits dynamics of few-cycle intense pulses in modern hollow-core "kagome" fibers filled with helium. Generation of new frequencies from soliton propagation in fibers is well known, but here a fundamentally new regime is exploited by using a) extremely short input pulses and b) highest possible intensities. After a few cm of propagation, such pulses will emit resonant radiation in the XUV range. The XUV pulses chirp can be compensated by linear propagation in a pre-ionized gas. Critical for success is the preparation of few-cycle short pulses of approx. 5 fs duration with around 20 µJ of energy, which will be accomplished by a home-built OPCPA setup.