Site selective spectroscopy of Yb3+ in NaT(WO4)2, T=Bi, Gd, Y, Lu, laser crystals: Assessment with simulated crystal field effects

The sequences of the energy levels of Yb3+ for the two different 2b and 2d crystal sites in tetragonal disordered double tungstate NaT(WO4)2, T = Bi, Gd, Y, Lu, laser crystals have been determined by 6 K site selective emission and excitation of the photoluminescence spectra. The results were assessed with predictive simulations of crystal field interactions for these Yb3+ sites in current NaT(WO4)2 hosts. The method allows the interpretation of low temperature optical absorption spectra containing unresolved information of all Yb centres in such disordered laser crystal hosts.