Room-temperature high-average-power strong-field terahertz source based on an industrial high-repetition-rate femtosecond laser

Free-space strong-field terahertz (THz) pulses, generated via optical rectification of femtosecond lasers in nonlinear crystals, are pivotal in various applications. However, conventional Ti:sapphire lasers struggle to produce high-average-power THz sources due to their limited output power. While kilowatt ytterbium lasers are increasingly adopted, their application in THz generation faces challenges: low optical-to-THz conversion efficiency (attributed to long pulse duration and low energy) and crystal damage under high pumping power. Here, we report a high-average-power strong-field THz source using a lithium niobate crystal pumped by a 1030 nm, 570 fs, 1 mJ, 50 kHz ytterbium femtosecond laser with tilted pulse front pumping (TPFP). By systematically optimizing TPFP implementations and comparing grating- and echelon-type configurations, we achieve a THz source with 64.5 mW average power at 42 W, 50 kHz pumping, and focused peak electric field of 525 kV/cm at 0.83 mJ, 1 kHz operation. Additionally, we observe Zeeman torque signals in cobalt-iron ferromagnetic nanofilms. This high-repetition-rate, high-average-power THz system, combined with its potential capabilities in high signal-to-noise ratio spectroscopy and imaging, promises transformative impacts in quantum matter manipulation, non-destructive testing, and biomedicine.