Growth, anisotropy, and spectroscopy of Tm3+ and Yb3+ doped MgWO4 crystals

Abstract

We report on an improved crystal growth process, reassessment of the orientation of the optical ellipsoid, and polarized spectroscopy of doped monoclinic magnesium monotungstate (MgWO₄) in a new dielectric frame. A set of crystals, including undoped, Yb³⁺-doped, and Tm³⁺-doped MgWO₄, were grown by the top-seeded solution growth (TSSG) method with K₂W₂O₇ as a solvent. This approach resulted in high-quality crystals with a significantly reduced growth time compared to those grown using Na₂WO₄. The crystal structures were confirmed by powder X-ray diffraction, and the lattice parameters were determined using Le Bail fitting. We review the growth methodology and emphasize the revision of the principal optical axes orientation in this biaxial crystal which differs substantially from previous reports. Polarized Raman spectroscopy was conducted based on this revised orientation. The absorption and stimulated emission cross-sections of the studied ions were derived for the principal light polarizations, comparing these findings with existing results to validate the new dielectric frame orientation.