Numerical Investigation of Broadband OPCPA Configurations for Direct Amplification of TW-Level, Two-Cycle Pulses

Generation of intense, isolated attosecond pulses [1] is the main motivation for the development of laser systems which are producing few-cycle, TW-level pulses [2-5]. The ELI-ALPS Single Cycle Laser (SYLOS) aims to provide 20 TW single cycle pulses at 1 kHz repetition rate [6]. Due to the requirements for stability and high average power the most promising approach for generating mJ-level, few-cycle pulses is noncollinear optical parametric chirped pulse amplification (NOPCPA) [2-5]. BBO and LBO are the two most favoured nonlinear materials in the visible and near-infrared spectral range, due to their broad gain bandwidth and high damage threshold. It was demonstrated that BBO and LBO can support 5.5 fs [4] and 7 fs [3] pulse durations respectively when 450 nm [4] and 515 nm [3] pumping was used. Even shorter, sub-5 fs pulse durations can be achieved by utilizing two-color pumping, that is, the second- and third-harmonic of a Nd:YAG pump laser in subsequent amplifier stages [2]. The latter solution is the most promising, however at 1 kHz repetition rate there is a risk of optics degradation due to high average power UV light.