Due to their high electrical-optical conversion efficiency, compact size and long lifetime, high power diode lasers have
found increased applications in many fields. As the improvement of device technology, high power diode laser bars with
output power of tens or hundreds watts have been commercially available. With the increase of high current and output
power, the reliability and lifetime of high power diode laser bars becomes a challenge, especially under harsh working
conditions and hard-pulse operations. The bonding technology is still one of the bottlenecks of the advancement of high
power diode laser bars. Currently, materials used in bonding high power diode laser bars are commonly indium and goldtin
solders. Experimental and field application results indicates that the lifetime and reliability of high power diode laser
bars bonded by gold-tin solder is much better than that bonded by indium solder which is prone to thermal fatigue,
electro-migration and oxidization. In this paper, we review the bonding technologies for high power diode laser bars and
present the advances in bonding technology for single bars, horizontal bar arrays and vertical bar stacks. We will also
present the challenges and issues in bonding technology for high power diode laser bars and discuss some approaches
and strategies in addressing the challenges and issues.
9xx nm CW mini-bar diode lasers and stacks with high brightness and reliability are desired for pumping fiber lasers and direct fiber coupling applications. For the traditional cm-bar with 1mm-2mm cavity, it can provide CW output power up to 80W-100W and high reliability, whereas the brightness is relatively low. In comparison, mini-bar based diode lasers with 4mm cavity offer a superior performance balance between power, brightness, and reliability. However, the long cavity and large footprint of mini-bar diode laser renders its sensitivity towards thermal stress formed in packaging process, which directly affects the performances of high bright mini-bar diode lasers. In this work, the thermal stress correlating with package structure and packaging process are compared and analyzed. Based on the experiment and analysis results, an optimized package structure of CW 60W 976 nm mini-bar diode lasers is designed and developed which relieves thermal stress.
High power diode lasers have been widely used in many fields. For many applications, a diode laser needs to be robust under on-off power-cycling as well as environmental thermal cycling conditions. To meet the requirements, the conduction cooled single bar CS-packaged diode laser arrays must have high durability to withstand thermal fatigue and long lifetime. In this paper, a complete indium-free bonding technology is presented for packaging high power diode laser arrays. Numerical simulations on the thermal behavior of CS-packaged diode laser array with different packaging structure were conducted and analyzed. Based on the simulation results, the device structure and packaging process of complete indium-free CS-packaged diode laser array were optimized. A series of high power hard solder CS (HCS) diode laser arrays were fabricated and characterized. Under the harsh working condition of 90s on and 30s off, good lifetime was demonstrated on 825nm 60W single bar CS-packaged diode laser with a lifetime test of more than 6100hours achieved so far with less 5% power degradation and less 1.5nm wavelength shift. Additionally, the measurement results indicated that the lower smile of complete indium-free CS-packaged diode laser arrays were achieved by advanced packaging process.