New applications were previously made available to diode lasers through the use of microcanal heat sinks — efficient cooling elements, but with strict cooling-water quality requirements. Jenoptik Laserdiode GmbH has unveiled tap-water-cooled quasi-CW diode laser stacks, which do not require deionized water for cooling. Many substances used in chillers, hoses and fittings are incompatible with deionized water, resulting in leakage and eventual system failure. The laser stacks can be operated with hard pulse mode, and they feature high optical output power and a lifetime of >20,000 h for industrial applications. They have applications in materials processing, in the medical field, and in the pumping of solid-state and fiber lasers.