Detailed Spectroscopic and Theoretical Analysis of Yb:LuAG Crystal at Cryogenic and Room Temperatures

By the analysis of the low-temperature absorption and emission spectra of the crystal 20% Yb³⁺:Lu₃Al₅O₁₂, the energies of the Stark levels of Yb³⁺ ion in dodecahedral positions are determined. Within the framework of the crystal field (CF) theory of point charges (D₂ point symmetry group), the CF parameters are determined, and the wave functions of the Stark states are constructed. The line strengths of indirect electric dipole and magnetic dipole inter-Stark transitions are calculated and the Judd–Ofelt parameters are determined. Low temperature absorption and emission spectra show a complex fine structure that cannot be explained on the basis of the standard level structure of Yb³⁺ occupying sites with dodecahedral crystal field symmetry.