High brightness fiber coupled diode lasers at 450 nm

With the advent of high power blue laser diodes in general and blue laser bars in particular new applications are emerging, utilizing this new technology. Possibly the biggest benefits compared to traditional high power diode laser wavelengths in the infrared spectral range are the improvements seen in copper welding applications, both in weld quality and overall process efficiency. A new generation of high power diode lasers with emission wavelengths near 450 nm is being developed at Coherent DILAS. These modules achieve high brightness levels combined with high power, suitable for materials processing applications. 500 W of optical output power from a 200 μm core fiber and 550 W from a 400 μm core fiber, each with an NA of 0.22, have been demonstrated. Modules are based on existing infrared product platforms already manufactured in high volume, allowing the usage of known-good processes and fully automated manufacturing equipment. At the same time, material costs are kept low, due to the large volume produced at other wavelengths. The main challenge in developing industrial grade laser modules in the blue spectral range is the required life time. While tremendous progress has been made in recent years, the chip material is still more sensitive to environmental factors compared to other high power diode laser bars. The issue is approached by Coherent DILAS in multiple ways with the goal of finding the best possible solution to minimize complexity in module design and operation, while meeting reliability requirements. Latest results, including life-test data under a variety of operating conditions, are presented.