Nonlinear absorption in lithium triborate frequency converters for high-power ultrafast lasers

We report on an analysis of the nonlinear absorption in lithium triborate (LBO) used for second and third harmonic generation of ultrashort laser pulses at average powers in the order of kW and with sub-picosecond pulse duration. Thermographic imaging of the LBO crystals together with a simple analytical model revealed the presence of nonlinear absorption in both harmonic generation processes. Subsequent processing with a numerical model considering the nonlinear mixing, the absorption, and the heat conduction was used to estimate the absorption coefficients. Average powers exceeding 100 W in the ultraviolet and 400 W in the visible spectral range were obtained while maintaining a good beam quality by avoiding excessive nonlinear absorption. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

This study reports on the analysis of nonlinear absorption in lithium triborate (LBO) for second and third harmonic generation. The absorption coefficients were estimated using thermographic imaging and numerical modeling, and high power harmonic generation results were obtained.