Researchers led by Profs. ZHANG Qingli and JIANG Haihe from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences have developed a high-symmetry gradient-doped Nd:YAG laser crystal designed for dual-end pumping configurations. This innovation significantly mitigates thermal effects and improves laser performance.

The results were published in Optics Express.

In solid-state laser technology, the thermal effect of the laser gain medium is a technical bottleneck that limits improvements in laser performance. Previous research has shown that gradient concentration crystals can effectively mitigate this issue. 

In this study, the researchers designed high-symmetry gradient-concentration Nd:YAG crystal rods by bonding two identical gradient-doped rods. In these rods, the dopant concentration gradually decreases from the center to both ends, forming a higher-doped center and lower-doped ends.

Operating at the same pump power, the high-symmetry, gradient-doped Nd:YAG crystal exhibited a significantly smaller temperature difference between its center and ends—approximately one-third of that observed in a conventional, uniformly doped crystal. The output was much higher, reaching over 14 W, and the efficiency was boosted by more than half. Even at moderate output levels, the crystal maintained noticeably better beam quality, producing a more stable and symmetrical laser beam than a uniformly doped crystal.

This work demonstrates the potential of high-symmetry gradient-concentration laser crystals as an exceptional gain medium for dual-end pumping.

Fig. 1. High symmetry crystal rods synthesis diagram and crystal rods. (Image by DOU Renqin)

Fig. 2. Schematic diagram of laser experimental setup for LD end-pumped (Image by DOU Renqin)