Exploration of the Crystal Growth and Crystal-Field Effect of Yb3+ in Orthorhombic GdScO3 and LaLuO3 Crystals

Yb3+-doped rare-earth sesquioxide crystals are a class of promising laser materials due to their high host thermal conductivity, but the insufficient emission bandwidth limits their applications in ultrafast pulsed lasers. Yb3+-doped orthorhombic mixed rare-earth sesquioxides show an effective spectral broadening based on the solid solution mixing strategy and indicate the development potential in ultrafast lasers. Herein, high-quality orthorhombic Yb:GdScO3 and Yb:LaLuO3 crystals were grown by optimizing the composition of raw oxide materials. Unlike the nearly standard stoichiometric cationic ratio in Yb:GdScO3, Yb:LaLuO3 shows a La/Lu ratio below 1, suggesting the presence of anti-site LuLa defects in the host lattice. The following spectral analysis and crystal-field calculation indicate that Yb:GdScO3 has only one kind of luminescent Yb3+ site, while Yb:LaLuO3 has four types of Yb3+ centers due to the anti-site effect. Furthermore, as for the same species of Yb3+-doped sites, Yb:LaLuO3 demonstrates nearly two times of inhomogeneous spectral broadening as that of Yb:GdScO3, which renders a more promising application value in ultrafast lasers. This study elucidates the importance of understanding the structure–activity relationship between different Yb3+-doped orthorhombic sesquioxides and might provide a feasible route for exploring Yb3+-doped ultrafast laser gain materials.