Abstract
Manipulating the atomic and electronic structure of matter with strong terahertz (THz) fields while probing the response with ultrafast pulses at x-ray free electron lasers (FELs) has offered unique insights into a multitude of physical phenomena in solid state and atomic physics. Recent upgrades of x-ray FEL facilities are pushing to much higher repetition rates, enabling unprecedented signal-to-noise ratio for pump probe experiments. This requires the development of suitable THz pump sources that are able to deliver intense pulses at compatible repetition rates. Here we present a high-power laser-driven THz source based on optical rectification in LiNbO3 using tilted pulse front pumping. Our source is driven by a kilowatt-level Yb:YAG amplifier system operating at 100 kHz repetition rate and employing nonlinear spectral broadening and recompression to achieve sub-100 fs pulses with pulse energies up to 7 mJ that are necessary for high THz conversion efficiency and peak field strength. We demonstrate a maximum of 144 mW average THz power (1.44 μJ pulse energy), consisting of single-cycle pulses centered at 0.6 THz with a peak electric field strength exceeding 150 kV/cm. These high field pulses open up a range of possibilities for nonlinear time-resolved THz experiments at unprecedented rates.
Highlights
Laser-based generation of high-field single- and multi-cycle terahertz (THz) pulses offers a powerful and widely accessible means of coherently driving atomic displacements or directly exciting specific low frequency modes to better understand collective mode and electron dynamics in a wide variety of materials [1–3]
We have demonstrated the generation of single-cycle THz pulses with energy up to 1.44 μJ at 100 kHz repetition rate
Our results are enabled by a unique pump laser source based on multi-pass spectral broadening and recompression delivering sub-100 fs pulses with close to 1 kW average power
Summary
Laser-based generation of high-field single- and multi-cycle terahertz (THz) pulses offers a powerful and widely accessible means of coherently driving atomic displacements or directly exciting specific low frequency modes to better understand collective mode (e.g., lattice) and electron dynamics in a wide variety of materials [1–3]. While accelerator-based sources can often provide higher pulse energies and a wider frequency tuning range, they are generally accompanied by high construction and operating costs, along with limited accessibility to researchers [4]. The higher repetition rate triggers challenges for the development of optical pump-probe lasers [14, 15], and opportunities to develop high power sources in the entire spectral range from UV to THz, used for optical pump-probe experiments. This work explores the generation of THz pulses at 100 kHz repetition rate, gives direction for power scaling, and proposes routes to obtaining higher THz conversion efficiencies. The compressed output (70-100 fs) is used for THz generation experiments
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