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J. Eur. Opt. Society-Rapid Publ. 22, 4( 2026)
The nonlinear crystal, most suitable for the high average power regime at multi-10-kHz repetition rates in the second stage, is OP-GaAs which, as a QPM material, has similar limitations in terms of available aperture as PPLN [ 1 ]. Apart from its numerous advantages in terms of extended transparency, nonlinearity and thermo-mechanical properties, OP-GaAs exhibits rather narrow pump acceptance bandwidth and will greatly benefit from the spectral narrowing achieved in the PPLN NRO [ 25, 26 ].
Further power scaling of the present NRO based on the large aperture 50-mm long PPLN crystal is obviously possible with more powerful( e. g., ~ 50 W) pump sources. Keeping the same pump levels in terms of fluence and intensity, e. g., at 20 kHz, from the comparison of the beam diameters in the two crystals employed in the present work, it is clear that the pump beam size in the large aperture PPLN can be simply increased by a factor of 1.5 which means that total energies exceeding 1 mJ and total average powers exceeding 20 W can be expected at similarly high conversion efficiency and minimum damage risk.
Funding
This project has received funding from DAAD( Germany) – DST( India) 2023-2025 project-related personal exchange programme( Grant no. 57683248) and the European Union’ s Horizon 2020 research and innovation programme under grant agreement no. 871124 Laserlab-Europe.
Conflicts of interest
The authors declare that they have no competing interests to report.
Data availability statement
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
Author contribution statement
Conceptualization, W. C., L. W, V. P. and R. M.; Methodology, W. C., L. W.; Software, G. S. and M. P.; Validation, T. T., S. D. and C. C.; Formal Analysis, W. C. and V. P.; Investigation, W. C., L. W., S. D. andT. T.; Resources, A. S., I. D., O. M., E. B., G. Z. and R. M.; Data Curation, C. C. and T. T.; Writing – Original Draft Preparation, V. P.; Writing – Review & Editing, V. P., W. C., M. P. and G. S.; Visualization, T. T., W. C., L. W. and C. C.; Supervision, V. P., W. C., R. M. andG. Z.; ProjectAdministration, V. P.; Funding Acquisition, V. P., S. D., and R. M.
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