Advance on the high power and high brightness diode laser modules for pumping and direct use applications

Industrial material processing represents a significant application for lasers. In this paper, we present our work on high power Diode Laser (DL) modules for the high brightness fiber laser pumping and direct diode laser integration. Together with state-of-the-art 915 nm and 976 nm Laser Diode (LD) single emitters from Coherent, we have realized an optical power 1200 W DL output (26 A driving current) with a 135 μm core-diameter fiber with a Numerical Aperture (NA) of 0.22 (power ratio of NA 0.19/0.22 ⪆95%). A dual wavelength combining technique was employed, yielding an fiber output brightness of 74 MW/(cm2•str). The fiber was end-capped to decrease the energy density on the optical coating. By adopting the same fiber end-capping optical coupling and wavelength combining techniques, a higher power DL module coupling 1800 W optical power into a 220 μm end-capped fiber was successfully fabricated. The module achieved a favorable balance between power and brightness, and its direct application potential was certified through spot welding of thin stainless-steel plates.