New laser properties and spectroscopy of orthorhombic crystals YAlO3:Er3+. Intensity luminescence characteristics, stimulated emission, and full set of squared reduced‐matrix elements |〈α[SL] J| |U(t)||α′[S′ L′] J′〉|2 for Er3+ Ions

New laser data on orthorhombic YAlO 3 :Er 3+ crystals are obtained. Stimulated emission in the 4 S 3/2 → 5 I 15/2 channel and cascase lasing of the sequential intermanifold 4 S 3/2 → 4 I 11/2 → 4 I 13/2 transitions are excited at 110 K with Xe-flashlamp pumping. Intensity absorption and luminescence characteristics of Er 3+ ions in the YAlO 3 crystal are experimentally determined and quantitatively analyzed in terms of the known semiempirical method. The intensity spectroscopic parameters Ω t obtained (Ω 2 = 0.95, Ω 4 = 0.58, and Ω 6 = 0.55 (in 10 -2 cm 2 )) nicely describe band-area intensities in the absorption spectrum of the YAl0 3 :Er 3+ crystal in the spectral region below 30000 cm -1 . A full set of reduced-matrix elements for the Er 3+ ions is calculated involving all 41 J-manifolds of the 4f 11 configuration lying in energy up to 97000 cm -1 . Using these data, the earlier reported intensity parameter Ω t for the YAlO 3 :Er 3+ crystal are revised and it is shown that involving highly excited levels of Er 3+ ions into intensity spectroscopic analysis leads to an overestimation of the parameters Ω 1 because of the possible presence of some additional absorption sources in the YAlO 3 host.