Polarized spectral properties and 2.3 µm laser performance of the Tm:YVO₄ crystal

The polarized spectral properties and ∼2.3 µm high-power continuous-wave laser operation of Tm³⁺-doped yttrium orthovanadate crystal (Tm:YVO₄) are reported. For the ³H₄ → ³H₅ transition, the stimulated-emission cross-section σ_SE is 1.01 × 10^-20 cm² at 2276 nm corresponding to a large emission bandwidth of 52 nm (for π-polarization). Pumped by a 794 nm laser diode, the 1.5 at.% Tm:YVO₄ laser delivered 5.52 W at 2.29 µm with a slope efficiency of 19.9%, a laser threshold of 8.70 W, and a linear laser polarization (π). The Tm laser operated on the cascade scheme (on the ³H₄ → ³H₅ and ³F₄ → ³H₆ transitions) which was mainly responsible for the observed high laser slope efficiency. We also report on the first passively Q-switched Tm:YVO₄ laser at 2.3 µm by employing porous nano-grained cuprous selenide (PNG-Cu₂Se) as a saturable absorber. The shortest pulse duration and the highest single pulse energy amounted to 706 ns and 3.65 µJ, respectively, corresponding to a pulse repetition rate of 62.8 kHz.