267-W cw AlGaAs/GaInAs diode laser bars

High-power 980 nm-diode laser bars have been fabricated in the AlGaAs/GaInAs material system. The bars are 1 cm wide and comprise 25 broad area lasers with 200 m aperture and 2 mm resonator length. Hence, the fill factor is 50%. To reduce the power density at the facet, we used an LOC structure with low modal gain, which also helps to prevent filamentation. The measured threshold current was 14 A and a record output power of 267 W cw was achieved at 333 A with an electro-optical conversion efficiency of 40%. With less thermal load, at 150 W output power the conversion efficiency was as high as 50% and the corresponding slope efficiency was 0.9 W/A. Microchannel copper heat sinks with a thermal resistance of less than 0.29 K/W were used for mounting the bars. The coolant temperature was set for all measurements to 22 °C and the flux was 0.9 l/min. Additionally, the top electrode of the p-side down mounted bars was cooled by a second heat sink, which was pressed gently on the top electrode.