22.5 W laser emission of Er:CaF₂ crystals at 2.8 μm

Power scaling of a continuous-wave (CW) bulk laser in the mid-infrared (Mid-IR) spectral region has been demonstrated employing a 2.5 at.% Er:CaF₂ crystal slab with double-end-pumping configuration and tailored pump beam profile for better geometry matching. A maximum output power of 22.5 W is achieved at 2.8 μm, corresponding to a slope efficiency of 29.4%. The M² -factor is 1.27 in the y-direction, compared to 10.29 in the x-direction. To the best of our knowledge, this presents the record power for end-pumped solid-state CW lasers in the 3-μm spectral range at room temperature. This work indicates that Er:CaF₂ crystals with a low doping level are promising candidates for high-power laser emission in the Mid-IR region.