Crystal Structure, Judd−Ofelt Analysis, and Spectroscopic Assessment of a TmAl₃(BO₃)₄ Crystal as a New Potential Diode-Pumped Laser near 1.9 μm

TmAl3(BO3)4 crystallizes in the trigonal system R32 (No. 155) with a = b = 9.2741(13) Å, c = 7.218(3) Å, α = β = 90°, γ = 120°, V = 537.7(2) Å3, Dc = 4.494 g cm-3, and Z = 3. The absorption spectrum of this crystal was recorded at room temperature. The Judd−Ofelt (J−O) theory was applied to the absorption intensities of TmAl3(BO3)4 to obtain the three J−O parameters: Ω2 = 2.40 × 10-20 cm2, Ω4 = 0.48 × 10-20 cm2, and Ω6 = 1.09 × 10-20 cm2. The radiative probabilities, radiative lifetimes, and branching ratios of TmAl3(BO3)4 were calculated. The absorption and emission cross sections, together with the potential laser gain near 1.9 μm, were investigated. The potential laser gain curves indicate that the tunability range is about 200 nm.