Diode-pumped high-power 1.9 µm and 2.3 µm cascade Tm:CALGO laser

We reported a diode-pumped high-power cascade Tm:CALGO laser simultaneously operating on the ³F₄ → ³H₆ (1.9 µm) and ³H₄ → ³H₅ (2.3 µm) Tm³⁺ transitions (non-competitive). For 1.5 at.% Tm³⁺ doping level, the cascade Tm:CALGO laser yielded a maximum total continuous wave laser output power of 6.95 W with a maximum slope efficiency of 40.3%. The ³F₄ → ³H₆ and ³H₄ → ³H₅ laser emissions corresponded to 4.89 W and 2.07 W with a maximum slope efficiency of 28.7% and 12.7%, respectively. To the best of our knowledge, the 2.3 µm laser power of 2.07 W represented the highest one amongst the (no) cascade Tm:CALGO lasers. Furthermore, the effect of the populations at the ³F₄ state on the 2.3 µm laser performance when the Tm:CALGO laser operated at the cascade state was demonstrated for the first time.