3D Printing of gradient-doped Yb:YAG laser ceramics by leveraging active mixing

Gradient-doped laser ceramics fabricated via 3D printing have great potential for high-power laser applications. However, it is challenging to produce such types of gain media because it is inconvenient to fabricate different component slurries prepared offline using traditional methods precisely. To address these issues, a facile approach for the additive manufacturing of high-power laser ceramics is proposed for gradient structure fabrication. First, a material-extrusion-based 3D printing device with a homemade active mixing module is developed to fabricate gradient-doped Yb:YAG(Y ₃Al ₅O ₁₂) laser ceramics using two slurries with different doping concentrations. Subsequently, the active mixing module is systematically investigated to obtain different Yb-doped concentrations of printing slurries with a uniform element distribution. By measuring the switching delay volume between different components, a proper volume adjustment enables the Yb concentration distribution of the green bodies to be consistent with the designed profile in the 3D process. Finally, multi-component (0–5–10–5–0 at% Yb:YAG) green bodies are printed, and experimental tests are conducted to evaluate the performance of these gradient-doped laser ceramics. The results show that the gradient-doped ceramic obtained 82.1% in-line transmittance at 1100 nm (4.6 mm thickness, along with the doping concentration gradient) and the average Yb ions diffusion distance across the interface fitted in the 20–30 μm range. Furthermore, a 1030 nm laser output with an output power of 4.5 W with a slope efficiency of 41.3% is achieved when pumped with a 940 nm laser diode. This study provides useful insights for developing various gradient rare-earth-doped laser ceramics for high-power laser applications.