High-average-power direct liquid-cooled Yb:YAG thin-disk oscillator

Thin-disk geometry offers large transverse dimension and superior thermal management, enabling the generation of high-energy, high-average-power laser pulses with good beam quality. The conventional Yb:YAG thin-disk gain module typically consists of a thin-disk bonded to a heat sink. Here, we present a direct-liquid-cooled Yb:YAG thin-disk structure as an alternative to the conventional gain module, in which the coolant flows directly over the thin-disk surfaces for heat extraction. A multipass pumping architecture is integrated into the gain module to ensure efficient pump absorption. This configuration enables efficient thermal management while maintaining low wavefront distortion. In oscillator experiments, we achieved 1700 W multimode and 500 W near fundamental mode continuous-wave laser output (M 2 < 1.5), corresponding to optical-to-optical efficiencies of 56.4 % and 38.5 %, respectively. These results demonstrate the promising potential of this structure for high-average-power laser operation with good beam quality and for compact multi-disk integration to scale output power and energy-storage capacity.