High-efficiency and reliable pump lasers for fiber lasers

Abstract

The demand for fiber lasers has increased due to widening of application areas and higher power levels. As fiber lasers have become the main workhorse for high power material processing applications and competition among fiber laser manufacturers have become more evident, the laser manufacturers are in the process to find ways to lower overall cost of ownership to become more competitive. Key areas to look at are the efficiency of the fiber laser, especially the efficiency of the diode pump modules, and the higher reliability of its’ components. There is increasing demand for high power, high brightness, and higher efficiency laser diodes for kW-level fiber laser pumping. We present high-efficiency and high brightness laser diode optimized for lowered operating voltage while maintaining high power conversion efficiency of 60%. The laser diode design is a single quantum-well InGaAs/AlGaAs structure with graded index profile and large optical cavity design. The laser is fabricated into 4 mm long chips with a 94 μm emitter stripe indented for standard 105/125 μm core fiber laser pumping. The chips are mounted on AlN carrier and characterized as chip-on-submount. The laser produces 12.6 W optical power at 13 A and 1.62 V, reaching 60% conversion efficiency at operating point. The beam divergence angles are 8.5° horizontal and 34° vertical enabling high brightness and efficient fiber coupling. Furthermore, the lasers are reliability tested where they show outstanding reliability without sudden failures and ware-out rate less than 1% per 1000 hour over several thousand hours of testing.