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Laser-driven particle acceleration is rapidly emerging as a mature technology enabling the development of compact and affordable accelerators for applications in several fields. Such applications would often benefit from the increase of the average particle flux, which is mostly dependent on the repetition rate of the underlying driver laser. Current technology of ultrashort, high peak power lasers is based on Ti:Sapphire (TiSa) amplification stages in Chirped Pulse Amplification (CPA) laser chains. Although recent technology developments are leading to the availability of TiSa lasers featuring J-level energy at 100Hz rep rate, such a technology doesn’t offer the prospect for substantial, further improvement in the available average power, requiring new approaches to more efficient laser amplifiers to be investigated.
At the Intense Laser Irradiation Laboratory (ILIL) of the National Institute of Optics of CNR (CNR-INO) in Pisa, the development of a new laser system targeting the kHz rep rate is currently ongoing. The laser exploits a recently proposed amplification scheme, based on the so-called Multi-Pulse Extraction (MPE) in long upper state lifetime active materials. This scheme enables a direct pumping of the active material with laser diodes, thus dramatically improving the thermal budget and the overall efficiency. In the scheme pursued at the ILIL lab, Tm:Lu2O3 ceramics are used as active media. Here we report on recent experimental measurements of the fundamental optical and atomic properties of this material [1], aimed at modeling the extraction limit and fundamental time behaviour of the gain, as well as on the design study and experimental development of a Tm-based CPA laser chain targeting 500mJ energy and 1kHz rep rate [2]. Direct pumping geometry and cooling architectures will be shown.
[1] Fregosi A, Brandi F, Labate L, et al. Cross-relaxation and temporal dynamics of lasing at 2 μm in thulium-doped ceramic material. High Power Laser Science and Engineering. 2025;13:e51. doi:10.1017/hpl.2025.37
[2] D. Palla, L. Labate, F. Baffigi, G. Cellamare, L.A. Gizzi. A model for pumping optimization in edge-pumped disk amplifiers. Optics & Laser Technology, Volume 156, 2022,108524, ISSN 0030-3992. doi.org/10.1016/j.optlastec.2022.108524.
