QCW laser diode bar stacks with improved performance and technology

We report recent improved QCW (quasi-continuous wave) laser diode (LD) bar stacks as pumping sources for applications such as inertial fusion energy research, high-energy solid-state lasers, and others. To effectively pump laser media, it is critical to enhance the output power, electro-optical conversion efficiency, and power density of the LD bar stacks. Recently, we developed a novel bonding technique for creating a high-power density LD bar stack structure, which has enabled stacking more than 50 LD bars with a narrow stacking pitch and operation with high injection current. We have demonstrated the highest peak output power of 56 kW and the highest power density of 29 kW/cm2 from a stack of 56 LD bars with 940 nm emission under the operating conditions of a repetition rate of 10 Hz, a pulse width of 0.3 ms, and an injection current of 1000 A at a water-cooled temperature of 20 °C. A maximum electro-optical conversion efficiency of 66% has achieved at an operating current of 450 A, and even 59% at an operating current of 1000 A.