Growth, structure, and polarized spectroscopy of monoclinic Er 3+ :MgWO 4 crystal

We report on the growth, structure, and polarized spectroscopy of a novel promising laser crystal, erbium-doped magnesium monotungstate, Er3+:MgWO4. 1.01 t.% Er3+:MgWO4 was grown by the Top-Seeded Solution Growth method using Na2WO4 as a solvent. The crystal structure was refined by the Rietveld method. Er3+:MgWO4 belongs to the monoclinic class (sp. gr. P2/c, wolframite-type structure, lattice parameters: a = 4.6939(6) Å, b = 5.6747(4) Å, c = 4.9316(6) Å and β = 90.7858(4) Å. The transition intensities for Er3+ ions were determined using the Judd-Ofelt theory accounting for an intermediate configuration interaction (ICI). Er3+ ions in MgWO4 exhibit intense, strongly polarized and broad absorption and emission bands owing to their accommodation in distorted low-symmetry sites (C2). The stimulated-emission cross-section for the 4I13/2 → 4I15/2 transition is 0.31×10−20 cm2 at 1637 nm (light polarization: E || b ). The radiative lifetime of the 4I13/2 state is 4.85 ± 0.05 ms. The multiphonon non-radiative relaxation for Er3+ excited multiplets is quantified. Er3+ ions in MgWO4 feature large Stark splitting of the ground-state, ΔE(4I15/2) = 435 cm-1. Er3+:MgWO4 is attractive for low-threshold lasers at ∼1.64 µm.