High-brightness laser diode arrays operating at a duty cycle of 10% - 20% are in ever-increasing demand for the
optical pumping of solid state lasers and directed energy applications. Under high duty-cycle operation at 10% - 20%,
passive (conductive) cooling is of limited use, while micro-coolers using de-ionized cooling water can considerably
degrade device reliability.
When designing and developing actively-cooled collimated laser diode arrays for high duty cycle operation, three
main problems should be carefully addressed: an effective local and total heat removal, a minimization of
packaging-induced and operational stresses, and high-precision fast axis collimation.
In this paper, we present a novel laser diode array incorporating a built-in tap water cooling system, all-hard-solder
bonded assembly, facet-passivated high-power 940 nm laser bars and tight fast axis collimation. By employing an
appropriate layout of water cooling channels, careful choice of packaging materials, proper design of critical parts, and
active optics alignment, we have demonstrated actively-cooled collimated laser diode arrays with extended lifetime
and reliability, without compromising their efficiency, optical power density, brightness or compactness.
Among the key performance benchmarks achieved are: 150 W/bar optical peak power at 10% duty cycle, >50% wallplug
efficiency and <1° collimated fast axis divergence. A lifetime of >0.5 Ghots with <2% degradation has been
experimentally proven. The laser diode arrays have also been successfully tested under harsh environmental
conditions, including thermal cycling between -20°C and 40°C and mechanical shocks at 500g acceleration. The
results of both performance and reliability testing bear out the effectiveness and robustness of the manufacturing
technology for high duty-cycle laser arrays.