Enabling high-power, broadband THz generation with 800-nm pump wavelength

The organic terahertz (THz) generation crystal BNA has recently gained traction as a source for producing broadband THz pulses. When pumped with 100 fs pulses, the thin BNA crystals can produce relatively high electric fields with frequency components out to 5 THz. However, the THz output with 800-nm pump wavelength is limited by the damage threshold of the material, particularly when using a 1 kHz or higher repetition rate laser. Here, we report that the damage threshold of BNA THz generation crystals can be significantly improved by bonding BNA to a high-thermal conductivity sapphire window. When pumped with 800-nm light from an amplified Ti:sapphire laser system, this higher damage threshold enables generation of 2.5x higher electric field strengths compared to bare BNA crystals. We characterize the average damage threshold for bare BNA and BNA-sapphire, measure peak-to-peak electric field strengths and THz waveforms, and determine the nonlinear transmission in BNA. Pumping BNA bonded to sapphire with 3 mJ 800-nm pulses results in peak-to-peak electric fields exceeding 1 MV/cm, with broadband frequency components >3 THz. This high-field, broadband THz source is a promising alternative to tilted pulse front LiNbO3 THz sources, enabling many research groups without optical parametric amplifiers to perform high-field, broadband THz spectroscopy. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

The use of organic terahertz crystal BNA bonded to a high-thermal conductivity sapphire window significantly improves the damage threshold and enables the generation of higher electric field strengths in THz output. This high-field, broadband THz source provides an alternative for research groups without optical parametric amplifiers to conduct high-field, broadband THz spectroscopy.