Assessing the influence of the vertical epitaxial layer design on the lateral beam quality of high-power broad area diode lasers

M. Winterfeldt; J. Rieprich; S. Knigge; A. Maaßdorf; M. Hempel; R. Kernke; J. W. Tomm; G. Erbert; P. Crump

doi:10.1117/12.2210838

4 March 2016 Assessing the influence of the vertical epitaxial layer design on the lateral beam quality of high-power broad area diode lasers

M. Winterfeldt, J. Rieprich, S. Knigge, A. Maaßdorf, M. Hempel, R. Kernke, J. W. Tomm, G. Erbert, P. Crump

Author Affiliations +

Proceedings Volume 9733, High-Power Diode Laser Technology and Applications XIV; 97330O (2016) https://doi.org/10.1117/12.2210838
Event: SPIE LASE, 2016, San Francisco, California, United States

Abstract

GaAs-based high-power broad-area diode lasers deliver optical output powers P_opt > 10W with efficiency > 60%. However, their application is limited due to poor in-plane beam parameter product BPP_lat=0.25×Θ_95%×w_95% (Θ_95% and w_95% are emission angle and aperture, 95% power content). We present experimental investigations on λ = 9xx nm broad area lasers that aim to identify regulating factors of the BPP_lat connected to the epitaxial layer design. First, we assess the thermal lens of vertical designs with varying asymmetry, using thermal camera images to determine its strength. Under study are an extreme-double-asymmetric (EDAS) vertical structure and a reference (i.e. more symmetric) design. The lateral thermal profiles clearly show that BPP_lat increase is correlated to the bowing of the thermal lens. The latter is derived out of a quadratic temperature fit in the active region beneath the current injection of the laser device and depends on the details of the epitaxial layers. Second, we test the benefit of low modal gain factor Γg₀, predicted to improve BPP_lat via a suppression of filamentation. EDAS-based lasers with single quantum well (SQW) and double quantum well (DQW) active regions were compared, with 2.5x reduced Γg₀, for 2.2x reduced filament gain. However, no difference is seen in measured BPP_lat, giving evidence that filamentary processes are no longer a limit. In contrast, devices with lower Γg₀ demonstrate an up to twofold reduced near field modulation depth, potentially enabling higher facet loads and increased device facet reliability, when operated near to the COD limit.

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M. Winterfeldt, J. Rieprich, S. Knigge, A. Maaßdorf, M. Hempel, R. Kernke, J. W. Tomm, G. Erbert, and P. Crump "Assessing the influence of the vertical epitaxial layer design on the lateral beam quality of high-power broad area diode lasers", Proc. SPIE 9733, High-Power Diode Laser Technology and Applications XIV, 97330O (4 March 2016); https://doi.org/10.1117/12.2210838

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