73% CW power conversion efficiency at 50 W from 970 nm diode laser bars

970 nm emitting diode laser bars of broad-waveguide design have been optimised for maximum power conversion efficiency (PCE). 73% PCE at 50 W CW output power is achieved from 20% fill-factor, 1 cm diode laser bars mounted on microchannel-cooled heatsinks. The improvement is mainly the result of an increase in injection efficiency via moderately low doping of the broad-waveguide core, and reductions in operating voltage via doping optimisation of the broad-waveguide structure.