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.