The photoluminescence property of pure and MgO co-doped near stoichiometric LiNbO3:Cr crystals has been investigated. It has been found that the presence of low Mg ion content in the crystals induces the coexistence of two types of Cr3þ sites; Cr3þ ion substituting Liþ and Nb5þ sites. In MgO co-doped samples, four narrow emission bands have been found and three of them are correlated with the broad absorption bands associated to the Cr3þ ions located in Nb5þ site (½CrNb centres). The observation of the zero-phonon line at 13 540 cm1 only in pure LiNbO3:Cr crystals of near stoichiometric composition suggests it could be used as a probe to monitor the composition of LiNbO3 crystals.
Han, T. P. J., Jaque, F., Bermudez, V., & Dieguez, E. (2003). Luminescence of the Cr3+ R-lines in pure and MgO co-doped near stoichiometric LiNbO3:Cr crystals. Chemical Physics Letters, 369(2003), 519-524. https://doi.org/10.1016/S0009-2614(02)02028-6