An output power of 1.55 W, the highest ever reported, at 20 °C has been achieved for a ZnCdSSe/ZnSSe/ZnMgSSe separate-confinement heterostructure laser diode under short-pulsed operation. A differential quantum efficiency of 28% and a maximum conversion efficiency of 1.5% were obtained. The output power was limited by catastrophic optical damage (COD) of the facets, as proved by atomic force microscopy (AFM).