Emission properties of Tm3+-doped CaF2, KY3F10, LiYF4, LiLuF 4 and BaY2F8 crystals at 1.5 μm and 2.3 μm.

Thulium ions (Tm3+) are known for their emissions in the near- and mid-infrared spectral ranges suitable for efficient laser operation. We systematically study the stimulated-emission cross-sections σ SE for the 3H 4 → 3F 4 (at ~1.5 μm) and 3H 4 → 3H 5 (at ~2.3 μm) Tm3+ transitions in five low-phonon energy fluoride single-crystals, namely, cubic Tm:CaF 2 and Tm:KY 3 F 10 , tetragonal Tm:LiYF 4 and Tm:LiLuF 4 and monoclinic Tm:BaY 2 F 8. A promising material is Tm:BaY 2 F 8 which offers broad and intense polarized emission spectra in the mid-infrared (2251–2452 nm); the maximum σ SE is 0.39 × 10−20 cm2 at 2289 nm (for E ||Z) and the emission bandwidth is exceeding 100 nm (for E ||X). We also revise the transition probabilities for Tm3+ ions in LiLuF 4 and BaY 2 F 8 crystals using the Judd-Ofelt formalism and accounting for an intermediate configuration interaction (ICI). • Stimulated-emission cross-sections for 3H 4.→3F 4 and 3H 4 →3H 5 thulium transitions; • Tm:CaF 2 , Tm:KY 3 F 10 , Tm:LiYF 4 , Tm:LiLuF 4 and Tm:BaY 2 F 8 fluoride crystals. • Tm:BaY 2 F 8 offers broadband and intense emission in the mid-infrared (2251–2452 nm). • In monoclinic Tm:BaY 2 F 8 , the maximum σ SE is 0.39 × 10−20 cm2 at 2289 nm. • Judd-Ofelt theory accounting for an intermediate configuration interaction (ICI). [ABSTRACT FROM AUTHOR]