Recent product releases of high power direct diode lasers in the blue spectral range of up to 1 kW of output power have sparked the demand for even higher optical output power for industrial copper welding applications, in particular related to e-mobility demands where high throughput is required. Blue laser bars maturing into a reliable technology present the ideal laser source for the task. While previously presented results of up to 500 W of output power from a 200μm NA 0.2 fiber were based on the Coherent ‘High Brightness’ product platform, the current work uses the ‘High Power’ product line, currently available with up to 8 kW of output power in the near infrared spectral range. This platform has the potential of reaching up to 4 kW of blue laser power from fibers with core diameters between 400μm and 800μm at wavelengths near 450nm. An increased number of laser bars compared to the existing product portfolio can achieve even higher output power. While the ‘High Brightness’ platform is based on mini-bars with 5mm length and designed for coupling into 200 μm core fibers, the ‘High Power’ product line uses 10mm wide laser bars. The focus lies on 400 μm core fibers in order to achieve high intensities at the work piece while maintaining a long working distance. However, for very high output power 600 μm and 800 μm fibers will be used. Here we present first results of the smallest laser module within the high power family with a goal of coupling 1500 W of optical power into a 400 μm NA0.22 fiber at an emission wavelength of approximately 450 nm. The product architecture and optical concept are described. Latest results showing 1.5 kW from a 600 μm core fiber at 5% duty cycle are presented and the next steps to reaching the goals of CW operation and 400 μm core size are discussed.
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.