In this letter, a high power, continuous-wave Tm:YAP InnoSlab laser has been developed. It produces 315 W of laser output power with an emission wavelength of 1.94 μm. The optical-to-optical efficiency and slope efficiency with respect to the absorbed pump power are 53.4% and 63.8%, respectively. At the output power of 300 W, the beam quality factors M 2 are 201 in the x-direction and 3 in the y-direction, respectively. The beam shape is rectangular, thus it is ideal for pumping a Ho:YLF laser crystal in InnoSlab design for oscillator and amplifier.

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.

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