Abstract

Making use of recent advances in high-average power femtosecond lasers for the generation of few-cycle THz sources with correspondingly high THz average power for THz-TDS with higher SNR and smaller measurement times has attracted significant research efforts in the last few years, with several results demonstrated recently, at different pulse energies and repetition rates [1,2]. The highest power demonstrated so far was 640 mW achieved with a broadband two-color plasma source, driven by a 570 W coherently combined fiber laser system, at 500 kHz repetition rate [2], corresponding to a THz pulse energy of 1.3 µJ. In this work, we present a record high-average power THz source based on the tilted-pulse front technique in lithium niobate at 80 K [3], delivering single-cycle pulses with (643±11) mW of average power at 40 kHz repetition rate, corresponding to a high THz pulse energy of 16.1 µJ. This was obtained at 400 W of pumping power obtained from a commercially available, thin-disk based regenerative amplifier (Trumpf Dira500), reaching a conversion efficiency of 1.6 · 10⁻³. We believe this type of source will have significant impact in the nonlinear THz spectroscopy community, enabling to reach strong fields in combination with high power spectral density in the sub-2 THz region, and accelerate measurement times by several orders of magnitude.

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