Sprecher
Beschreibung
Modern high-intensity laser systems are required to provide higher repetition rate, greater stability and higher output energy with increased wall-plug efficiency. In recent years, diode pumping has become a central theme in the development of new laser systems. With narrowband emission and precise current control, laser diodes offer higher efficiency and more stable output than flashlamp-pumped solid-state lasers, making them an attractive choice. Novel laser gain media and advancements in laser diode technology set the stage for the development of these new amplifier systems [1, 2].
The Petawatt High-Energy Laser for Heavy Ion EXperiments (PHELIX) located at GSI Helmholtz Centre for Heavy Ion Research is actively exploring pathways for future capability upgrades, such as transitioning to diode-pumped architectures in the early amplification chain. Serving as the initial stage of the high-intensity beam line, the femtosecond frontend delivers a pre-amplified seed pulse in the mJ range. Currently, it relies on a Ti:Sapphire based ring regenerative amplifier, exploiting the ultra broadband emission up to the central wavelength of the Nd:Glass main-amplifier at 1053 nm [3, 4]. This gain medium, while effective, requires expensive, bulky, frequency doubled pump lasers and is unfeasible for diode pumping [5].
A promising material that allows both, diode pumping and emission in the relevant spectral range of PHELIX is $\mathrm{Yb}{:} \mathrm{CaGdAlO_4}$ (Yb:CALGO) [2]. It is worth noting that the choice of material for broadband emission at 1053 nm is quite limited. To the best of our knowledge, Yb:CALGO shows the best compromise, justifying the move towards an experimental demonstration. As a precursor to this, we numerically modeled the pumping and amplification processes for three distinct cavity layouts to evaluate the feasibility of a Yb:CALGO-based amplifier for PHELIX. Our results indicate that achieving 20 mJ output energy is feasible, satisfying the requirements to replace the current amplifier.
Here, we present the theoretical design and simulation of a Yb:CALGO regenerative amplifier proposed as the successor to the Ti:sapphire-based stage and discuss its output characteristics.
[1] M. F. Kling et al., Roadmap on basic research needs for laser technology, J. Opt., 27(1):013002 (2025),
DOI: 10.1088/2040-8986/ad8458.
[2] H. Wang et al., Advances of Yb:CALGO Laser Crystals, Crystals, 11(9):1131 (2021),
DOI: 10.3390/cryst11091131.
[3] Z. Major et al., High-energy laser facility PHELIX at GSI: latest advances and extended capabilities, High Power Laser Science and Engineering, 12:e39 (2024),
DOI: 10.1017/hpl.2024.17.
[4] Y. Zobus, Design and implementation of a high-contrast, millijoule-level ultrafast optical parametric amplifier for high-intensity lasers, PhD thesis, Technische Universität Darmstadt (2023),
DOI: 10.26083/tuprints-00024200.
[5] P. F. Moulton, A. R. Fry, and P. Fendel, Ti:sapphire: Material, Lasers and Amplifiers, in Handbook of Laser Technology and Applications, CRC Press (2021),
DOI: 10.1201/9781003127130.
