By optimising mirror reflectivities, number of quantum wells, and miff or doping, record continuous wave (CW) output power levels and low threshold currents have been achieved. Broad area devices yielded > 12 mW CW and > 500 mW pulsed, 6-mu-m devices gave submilliampere threshold currents and output power > 1 mW and 10-mu-m devices showed output powers > 3 mW with a threshold of 1.5 mA.