Integrated transmission-reflection strong-field terahertz time-domain spectroscopy

Strong-field terahertz time-domain spectroscopy (THz-TDS) is an effective tool for material testing, non-destructive testing, and modulation device measurement. Strong-field THz waves advance non-equilibrium perturbation, quantum material manipulation, and biomedical research, but their systems are long constrained by strong-field THz sources' performance limits and high costs. Here, we present a high-repetition-rate integrated transmission-reflection strong-field THz-TDS, driven by an industrial Yb-doped femtosecond laser (1,030 nm, 0.8 mJ, 570 fs, 1-50 kHz tunable repetition rate). It achieves 1.14 μJ single-pulse THz energy (>403 kV/cm focal peak field), 43 mW average power (50 kHz), and ∼60 dB signal-to-noise ratio (SNR) for both modes. Verified by high-resistivity silicon wafer thickness profiling and THz field-sensitive metasurface testing (100 GHz frequency shift under THz field change), it enables nonlinear excitation and strong-field spectroscopy. Compared to Ti:sapphire-driven systems, it has comparable THz field at a lower cost, higher power, and faster measurement potential, promising broader practical applications.