Advances in Diode Laser Bar Power and Reliability for multi-kW Disk Laser Pump Sources

The industrial laser market has rapidly expanded over the past decade with the emergence of advanced high brightness solid state laser technology. Thin disk laser systems are important examples of these powerful tools enabling a range of high-end CW materials processing applications such as 2D sheet metal cutting and remote welding applications, and the rising demand for a range of demanding high-energy pulsed applications of high average power. Commercial applications with power in the range of 8 kW-20 kW can be cost competitive using disk lasers in moderate volumes compared to more commoditized solid-state laser sources such as fiber lasers. Reduction in the cost structure of disk laser pump sources requires an increase in brightness, efficiency and power of diode lasers bars within. Here we show the development of thin disk laser pump modules from an original common cooler platform with similar to 180 W per laser bar to recently developed individually cooled laser bars each operating continuously over 300 W. We demonstrate pump modules utilizing these bars with total power of up to 2.4 kW at 940 nm. Cooling in such laser modules is provided by mounting laser bars on isolated laser coolers (ILASCO). The ILASCO cooler comprises a multi-layer structure of aluminum nitride and copper sheets that are designed to decouple the direct current path from the water cooling eliminate electro-corrosion and to maximize heat dissipation and match the thermal expansion of the diode laser bar. We demonstrate advances in the single quantum well InGaAs/AlGaAs laser epitaxy design and chip layout that enables high power operation at operating temperatures up to 80 degrees C. We show increase in peak electro-optic efficiencies from 55% to over 60% at this temperature. With the application of advanced facet passivation technology, we demonstrate >35 khr reliable operation in the application through accelerated aging tests.