Spectral characteristics of the thulium ion and cascade generation of stimulated radiation in a YAIO3:Tu3+:Cr3+ crystal

Stimulated emission was obtained from Tu³⁺ ions in YAIO₃ crystals doped with 1.0 at.% Tu and 0.1 at.% Cr. The stimulated radiation was generated by the ³F₄→³H₅(λ₁)→³H₅→³H₆(λ₂) cascade at wavelengths λ₁ = 2.34 μ and λ₁=1.93 μ and the threshold was 3.5 J/cm at 90 °K. A scheme of radiative and nonradiative transitions between the terms was constructed. The absorption and luminescence spectra recorded at 4.2 °K were used to derive the Stark splitting scheme of the ³H₄ and ³H₆ terms of the thulium ion.