Brightness and efficiency scaling of a 1kW direct diode laser module emitting at 780 nm for additive manufacturing of aluminum

A 1 kW continuous wave 780 nm diode laser process head for industrial additive manufacturing of aluminum is presented. This process head combines and focuses the beams of two stacks, each consisting of 24 sandwich-mounted wide-aperture diode lasers. Heat from the emitters is efficiently extracted via micro-channel-free water coolers soldered to the sides of the laser stacks. The compact and light-weight module (21 cm × 29 cm × 61 cm, 12.5 kg) can be mounted directly to a robotic arm, eliminating the need of a failure prone optical fiber and enabling long-stretch processing and operation in confined spaces. We present and compare the results of a brightness and efficiency improved module iteration. By optimizing the chip design for 1 kW operation, we were able to increase the efficiency from 33 % to almost 50 % and double the brightness to 2 kW / mm² by reducing the spot size from 1 mm² to 0.5 mm². We also demonstrate that we can transfer this performance to 793 nm stacks, allowing the module to be used directly as an efficient pump source for Tmdoped solid-state lasers or to scale it up with wavelength beam combining to a 2 kW process head. At the end, we show the results of the first successful AM trials with the first generation of our process head.