Advances in manufacturing technology for low cost QCW diode laser stacks suitable for high energy pumping applications

Abstract

We report a novel approach for the assembly of monolithic diode laser stacks with up to 56 laser diode bars at 0.48mm pitch. These stacks are based on 940nm laser bars AuSn soldered on CuW-submounts. By joining the 56 bar-on-submounts (BoS) using an electrically conductive material the complete continuous stack is formed. A robot is used to load these BoS into fixtures for the bonding process. We show the attachment of this monolithic stack to an insulated micro-channel cooler using electrically insulating bonding material to complete the laser module. Use of the novel bonding materials at lower joining temperatures, compared to conventional soldering processes, results in a stack assembly with lower induced stress which allows monolithic stacks with higher number of elements. We demonstrate peak power above 500W per bar at 0.3% duty cycle and 500A peak current with an average junction temperature of 45°C, with over 29kW total peak power. Analysis of the dynamic temperature behavior within the pulses is presented using fast spectral measurements and simulation along with initial reliability test results.