We demonstrate a technique for collimating conduction-cooled QCW diode laser stacks that achieves very high brightness in a compact and robust package. First we collimate the bars in the fast-axis using a pre-aligned array of Doric GRIN cylindrical lenses, where each lens is oriented to correct the gross positioning errors of each bar. We then measure the residual beam errors using a proprietary wavefront mapping system, and fabricate a refractive wavefront correction phaseplate to effectively flatten the wavefront. The type of lens used exhibits particularly low aberration in the presence of misalignment, ensuring that the resultant wavefront can be effectively corrected. We applied the technique to two 0.5 mm pitch, 12-bar stacks operating at 1.2 kW. By this method, we repeatably obtained a 10-fold increase in stack brightness, reducing fast-axis beam divergence for the entire stack to below 0.3°, close to the theoretical limit. The result is an extremely compact, high brightness source optimised for side-pumping thin slab lasers.

Date Published: 25 February 2008
PDF: 10 pages
Proc. SPIE 6876, High-Power Diode Laser Technology and Applications VI, 687602 (25 February 2008); doi: 10.1117/12.765485

Published in SPIE Proceedings Vol. 6876:
High-Power Diode Laser Technology and Applications VI
Mark S. Zediker, Editor(s)