Thermal Lens Manipulation Using Edge-Heaters in Laser Bars for Improved Efficiency and Divergence
Md. J. Miah1, A. Boni2, D. Martin3, A. Ginolas3, M. Elattar3, P. Della Casa3, S. Grützner4, S. Strohmaier4, A. Knigge3, G. Tränkle3, and P. Crump3
Published in:
IEEE Photonics Technol. Lett., vol. 37, no. 9, pp. 545-548 (2025).
Abstract:
We present here an approach to flattening the lateral thermal lens that develops in kW-class semiconductor laser bars consisting of multiple broad-area emitters and is responsible for limiting the power, conversion efficiency and beam quality of the bars. Simulation results show that by increasing heat at the edgeemitters of the bars, thermal lens can be diminished. With an experiment on single-emitters, we demonstrated that the required heat in the edge-emitters can be achieved by shortening their pump length. Following these studies, we fabricated 1-cm wide bars containing 37 emitters, each with a 186-µm-wide stripe and a 4-mm-long resonator. In contrast to the baseline bars with equally and fully pumped emitters, the best-designed bars with an optimum (shorter) pump length only in the edge-emitters yield a 5%-points higher conversion efficiency, and an improved beam quality, narrowing the lateral beam divergence at 95% power content by over 10% at 0.8 kW power.
1 Institute of Information and Communication Technology, Bangladesh University of Engineering and Technology, Dhaka 1205, Bangladesh
2 Lumics GmbH, 12681 Berlin, Germany
3 Ferdinand-Braun-Institut (FBH), 12489 Berlin, Germany
4 TRUMPF Laser GmbH, 12489 Berlin, Germany
Index Terms:
Laser bars, high-power lasers, beam quality, edge heaters, beam divergence.
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