Tailored in-plane thermal profiles for narrower lateral far-field in kilowatt-class 9xx nm diode laser bars

Md. Jarez Miah; Matthias M. Karow; Mohamed Elattar; Dominik Martin; Pietro Della Casa; Stefan Grützner; Stephan Strohmaier; Andrea Knigge; Paul Crump; Günther Tränkle

doi:10.1117/12.2648355

14 March 2023 Tailored in-plane thermal profiles for narrower lateral far-field in kilowatt-class 9xx nm diode laser bars

Md. Jarez Miah, Matthias M. Karow, Mohamed Elattar, Dominik Martin, Pietro Della Casa, Stefan Grützner, Stephan Strohmaier, Andrea Knigge, Paul Crump, Günther Tränkle

Author Affiliations +

Proceedings Volume 12403, High-Power Diode Laser Technology XXI; 124030I (2023) https://doi.org/10.1117/12.2648355
Event: SPIE LASE, 2023, San Francisco, California, United States

Abstract

High-power, efficient semiconductor laser bars are demanded in many applications including pumping solid-state lasers and fibers. A narrow beam divergence is essential for increasing coupling efficiency and realizing an overall simple, cost-effective system. In kilowatt-class laser bars with 4 mm resonator length containing multiple broad-area emitters (with stripe width varying within 90–1200 μm) that are fabricated using conventional processing techniques, a strong thermal lens is generated within the individual emitters during laser operation. The lensing effect becomes stronger with increasing operating power. This allows a large number of lateral modes to be guided within the resonator and contribute to the laser emission, consequently deteriorating the beam quality (i.e. leading to larger lateral beam divergence angle). An approach to reduce the lateral divergence of the bar by modifying the in-plane structure of the emitters is presented. Based on simulation results, multiple lateral emitter structures have been developed and measured in quasi-continuous wave mode at low and high heat conditions with thermal resistance of 0.02 K/W and 0.05 K/W, respectively, comparable to continuous-wave testing with advanced coolers. Experimental results show that the improved lateral structures lead to enhanced power-current performance and improved beam divergence. A reduction of around 20% (~2°) in the bar lateral beam divergence angle at 95% power content has been achieved in testing at 800 W, with a simultaneous 5%-points gain in conversion efficiency with the highest performance lateral emitter structure.

Conference Presentation

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Md. Jarez Miah, Matthias M. Karow, Mohamed Elattar, Dominik Martin, Pietro Della Casa, Stefan Grützner, Stephan Strohmaier, Andrea Knigge, Paul Crump, and Günther Tränkle "Tailored in-plane thermal profiles for narrower lateral far-field in kilowatt-class 9xx nm diode laser bars", Proc. SPIE 12403, High-Power Diode Laser Technology XXI, 124030I (14 March 2023); https://doi.org/10.1117/12.2648355

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