Yb:YAG thin-disk regenerative amplifier laser system emitting > 500 W average power and and 800-fs long pulses with 50 mJ pulse energy at 1030 nm.

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Coherent sources of ultrashort THz pulses based on down-conversion of near-infrared laser pulses have seen enormous progress in the last few decades. This progress has enabled time-domain THz spectroscopy to emerge as a powerful tool for a wide variety of applications. ranging from the study of temporal dynamics of fundamental constituents of matter in physics and chemistry, to more applied topics such as drug or explosives detection. However, all these applications are currently strongly limited by the consistent lack of sources emitting energetic THz pulses with high average power, particularly in the frequency region [1-10 THz]. A limited average power of THz-TDS means that an undesired compromise between THz pulse energy and repetition rate needs to be met, which in turn means either abandoning research lines where energetic pulses are needed, or sacrificing repetition rate in the few cases where this is a possibility. These limitations occur because most THz-TDS setups are nowadays driven by near infrared Ti:Sapphire laser systems, which are limited in average power to only few watts. Since the conversion efficiency from near infrared to THz does typically not exceed a few percent, reaching significantly higher average powers in the THz regime requires driving ultrafast laser sources with much higher average power.We are therefore applying here for a state-of-the-art near-infrared ultrafast regenerative laser amplifier (Yb:YAG, 1030 nm) system based on the thin disk laser technology, which provides a unique combination of high repetition rate (5 – 50 kHz) and very high pulse energy (up to 50 mJ), thus operating with two orders of magnitude higher average power (> 500 W) than their Ti:Sa counterparts. This laser system will be used on the one hand for exploring two-color filamentation at high-repetition rate for the generation of broadband and strong-field Terahertz pulses in the [1-10 THz] region, but also for generating mJ-class THz pulses at <1 THz using titled-pulse fronts in Lithium Niobate. Thanks to the unique performance of the source we target to purchase, we expect to achieve watt-level, broadband THz pulses in the [1-10 THz region] with >1 µJ pulse energy - performance which remains unpaired in a laboratory setting to the best of our knowledge - as well as record high-energy single-cycle THz pulses with unprecedented high repetition rate in the < 1 THz region. This will complement our ongoing research on high-power THz sources by providing significantly higher pulse energy, thus enabling groundbreaking research in the field of nonlinear THz spectroscopy, in particular in the unexplored field of nonlinear THz spectroscopy of water and other samples in biological conditions.