M. Wilkens, G. Erbert, H. Wenzel, A. Maaßdorf, J. Fricke, A. Knigge and P. Crump

Published in:

Conf. on Lasers and Electro-Optics/Europe and European Quantum Electronics Conf. (CLEO/Europe-EQEC 2021), Munich, Germany, Jun. 21-25, virtual event, ISBN: 978-1-6654-1876-8, cb-p-2 (2021).

Abstract:

Dense wavelength beam combining (DWBC) techniques can be used to image many diode lasers into a single beam with minimal degradation of beam quality M²_95% (at 95% power) and conversion efficiency η_E. Systems based on DWBC of broad area lasers can be scaled into the many-kW class for use in material processing applications [1] . Laterally single mode diode lasers with wavelength around λ = 970 nm that use advanced waveguide designs (with lateral mode filter and extremely asymmetric vertical design) offer a path to much higher brightness [2] . Such lasers achieve high power P_opt and efficiency η_E in continuous wave CW (P_opt = 1 W, η_E = 65%, M²_95% < 1.1) [3] and pulsed (P_opt = 18W, 3.3 ns 10 kHz, M²_95%  < 2.2) [4] operation, whilst remaining close to the diffraction limit. When external λ-stabilization is performed via a diffractive element (grating), the operating characteristics are strongly affected by the interaction between external optical configuration and internal diode laser design, seen in P_opt , η_E, spectral width Δ λ_95% (at 95% power), λ-tuning range and beam stability. The λ-tuning range and Δ λ_95% for each diode laser are especially important as this limits the number of emitters that can be combined and thus the maximum achievable power via DWBC.

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