12.7 W intra-cavity pumped Ho:YAG laser with near-diffraction-limited beam quality

We demonstrated a compact and efficient Ho:YAG slab laser intra-cavity pumped by a Tm:YLF slab laser for the first time. In the Tm:YLF laser operation, the maximum power of 32.1 W with optical-to-optical efficiency of 52.8% was obtained. In the intra-cavity pumped Ho:YAG laser operation, the output power of 12.7 W at 2122 nm was obtained. The beam quality factors M² in the vertical and horizontal directions were 1.22 and 1.11, respectively. The RMS instability was measured to be lower than 0.1%. To the best of our knowledge, this was the maximum power for the Tm-doped laser intra-cavity pumped Ho-doped laser with near-diffraction-limited beam quality.