The optical absorption and fluorescence of ${\mathrm{Pr}}^{3+}$ ion in ${\mathrm{LiNbO}}_3$ has been systematically investigated. This system is characterized by a very intense red emission at 620 nm corresponding to the ${}_{}{}^1{}_{}{}^{}$${\mathit{D}}_2$${\to }^3$${\mathit{H}}_4$ transition. The luminescence of the metastable ${}_{}{}^3{}_{}{}^{}$${\mathit{P}}_0$ state is almost completely quenched in contrast with other materials. The nonradiative deexcitation has been analyzed for the ${}_{}{}^1{}_{}{}^{}$${\mathit{D}}_2$ multiplet in terms of a multiphonon process, and a quantum efficiency of 0.87 is experimentally deduced for this state at room temperature. Fluorescence quenching of ${}_{}{}^1{}_{}{}^{}$${\mathit{D}}_2$ is observed when concentration is increased, and a cross-relaxation process is proposed for concentrations above 0.09 mol %. The fluorescence decay time functions are well explained in the frame of the Inokuti and Hirayama model considering mainly an electric dipole-dipole interaction. It has been also concluded that praseodymium ions are randomly distributed in the ${\mathrm{LiNbO}}_3$ host, so that local charge compensating Pr(${\mathrm{Li}}^{+}$)-Pr(${\mathrm{Nb}}^{5+}$) pairs must be disregarded.

• Received 3 February 1995

DOI:https://doi.org/10.1103/PhysRevB.51.16643