Four-wavelength laser operation of Tm:YVO4 crystal: Transition assignment of the 2.17 μm laser emission

We reported the first demonstration of a diode-pumped Tm:YVO 4 laser simultaneously operating at 1.9 μm, 2.17 μm, 2.29 μm, and 2.37 μm. For the intermediate 2.17 μm laser emission, located between the purely electronic 3 F 4 → 3 H 6 and 3 H 4 → 3 H 5 transitions, the transition assignment was studied in detail by rationally designing the coating curves of the cavity mirrors. A distinct “see-saw” relationship was observed between the 1.9 μm and 2.17 μm laser output powers, indicating the strong gain competition between the two laser emissions. We conclude that the strong gain at 2.17 μm may primarily originate from the phonon-assisted 3 F 4 → 3 H 6 transition, with negligible contribution from the purely electronic 3 H 4 → 3 H 5 transition. Based on the Raman spectrum of the YVO 4 crystal and the Stark splitting of Tm 3+ multiplets in YVO 4 , the vibronic energy level was postulated. This work presented the first investigation into the transition assignment of the 2.17 µm laser emission for the Tm:YVO 4 crystal.