Our goal in demonstrating high-power few-cycle THz sources is to advance solvation science by elucidating the microscopic dynamics of solvents, particularly water, in bulk and chemical reactions like protein folding. THz radiation, with photon energy of 1-10 THz, is ideal for probing water’s hydrogen bond network motions. While THz-TDS studies of liquids are growing, they mostly use linear techniques, offering limited dynamic range with long experimental runtimes. Nonlinear THz spectroscopy is the next milestone but requires high-energy, high-repetition-rate THz sources. Current limitations include low pulse energy at high repetition rates or long measurement times at low repetition rates, especially for liquids due to weak nonlinear responses and strong absorption.

To overcome these challenges, we utilize a state-of-the-art  THz sources driven by a regenerative amplifier (TRUMPF Scientific Lasers, DIRA 500-10) , which provides up to 500 W of average power at repetition rates of 10, 40, and 100 kHz. This unique combination of high average power and variable repetition rates grants us access to two distinct regimes of high interest: high energy at moderate repetition rates and moderate energy at high repetition rates, all while maintaining a consistent 500 W average power. This flexibility enables us to tailor our experimental conditions to the specific requirements of our research.

To ensure the optimal performance of our laser source, we employ an autocorrelator to continuously monitor its specifications, allowing us to track any changes in real-time. Additionally, we have implemented an external PID-loop controlled beam stabilization system, which significantly improves the beam pointing stability. This enables us to work at nearly turn-key conditions, with the setups remaining aligned and requiring only little adjustments while operating at average powers of this level.

Our research efforts are currently focused on developing THz sources based on optical rectification, a promising approach that holds great potential for advancing the field. Furthermore, we are exploring the possibility of combining our laser source with external temporal pulse compression techniques to create ultra-broadband air-plasma based THz sources. These sources are expected to achieve unprecedented pulse energies and average powers with octave-spanning spectral bandwidths, paving the way for groundbreaking discoveries in solvation science and beyond. By pushing the boundaries of THz technology, we aim to unlock new insights into the complex dynamics of solvents and chemical reactions, ultimately driving progress in our understanding of these fundamental processes.