Some things have changed since one year due to the COVID pandemic. So also the participation in national and international conferences. Nevertheless, research continued and great successes were achieved. They become visible, among other things, through awards from the scientific community and at the same time motivate the researchers for further efforts.
Therefore, especially in these times, it is a particularly pleasant success that the PhD students Henning Stark and Albrecht Steinkopff were honored for their research work with the first and third place of the Best student paper of the sub-conference "Fiber Lasers XVIII: Technology and Systems".
Henning Stark presented a large-bandwidth, high-power, high-pulse-energy fiber laser system based on the coherent beam combination of 16 ytterbium-dopedrod- fiber amplifiers. A novel two-staged and partially helium-filled CPA grating compressor allows compression of the amplified pulses while maintaining a nearly diffraction-limited beam quality. Two laser operation regimes were investigated, with one targeting the shortest possible pulse duration, achieving 106 fs at an average power of 910 W and a pulse energy of 910 μJ. In a second experiment, the average power was successfully increased to 1 kW and the pulse energy to 10 mJ, with the pulse duration optimized to 120 fs. Both results represent record values for fiber CPA systems! For this, 1st place was awarded accordingly: "I am of course very proud that we were able to achieve such results together as a team! Even though we were not able to present our results in person and on site, everyone definitely made the best of the current situation," says Henning Stark.
Albrecht Steinkopff focused on theoretical considerations for the performance and energy scaling of coherently combined multicore fiber amplifiers. In his simulations, he compared co- and counter-pumped fibers with squarely arranged cores (2x2 to 10x10). He was able to show that increasing the number of cores favors power and energy extraction, but causes thermal effects. These lead to asymmetric mode shrinkage and consequently to a degradation of the combination efficiency. These effects were the main component of his comprehensive study. Albrecht Steinkopff additionally presented strategies to counteract these thermal effects and was able to show that this enables further performance and energy scaling of multicore fibers. "Next, we want to confirm these conclusions in the laboratory," he said. "We are confident to present our experimental findings at Photonics West next year," Albrecht Steinkopff is pleased to say.