Abstract

High-intensity THz sources driven by ultrafast lasers are attractive for a wide range of applications such as time domain spectroscopy, molecular dynamics and THz-matter interactions in the nonlinear regime, to cite a few. Recent advances in the development of high-average power ytterbium lasers have enabled the development of high-repetition rate THz-sources using different generation schemes. The best performances have been reached in a two-colour plasma generation setup driven by a state-of-the-art Yb fibre laser system and producing 640 mW THz average power at 500 kHz repetition rate [1]. However, this facility is complex and expensive as it implies few-cycle pump pulses with high average powers. The second promising approach for high power THz generation is based on optical rectification in lithium niobate (LiNbO₃) nonlinear crystals [2]. In particular, it has been demonstrated that optimization of the pump pulse duration to few hundred femtoseconds in a tilted-pulse front pumping scheme in lithium niobate using a step-stair echelon is a relevant approach for optical-to-THz conversion efficiency scaling [3,4]. Single-cycle THz pulses with 74 mW average power and 400 kV/cm peak intensity have then been produced using a 10W-class pump laser delivering 240 fs pulses at 25 kHz repetition rate [4].

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