Abstract

The vast majority of HHG sources are nowadays driven using Ti:Sapphire lasers that typically generate 30 fs pulses with few mJ energy at 1 kHz repetition rate and 800 nm wavelength, corresponding to average powers limited to around 10 W. Nonlinear compression of these sources leads to the few-cycle regime with pulse durations below 5 fs [1]. Nowadays another approach is to use femtosecond rare earth-doped fiber amplifiers that are capable of generating kW average powers [2]. In this case, gain narrowing limits the pulse duration of high energy fiber CPA to above 250 fs, and accessing the few-cycle regime requires two stages of nonlinear compression [3].

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