Growth and characterization of lithium tantalate single crystals doped with Ho, Tm, Nd, Yb, Pr and doped by diffusion with Cr and Cu

Crystal growth conditions for lithium tantalate single crystals doped with rare-earth and conditions of the diffusion process for doping with Cr and C u are described. Absorption and an additional absorption after gamma-irradi ation and annealing treatments at room temperature were measured. The gamma -irrdiation with a dose of 10(5) Gy and subsequent annealing at 800 degrees C in air for 3 h lead to a valency change of Ho and Pr ions. In the case o f gamma-irradiation a recombination process due to the Compton effect seems to be responsible for the valency change process in both crystals. Lumines cence and radioluminescence measurements in UV + VIS range were also perfor med which show a weak excitation energy transfer from the LiTaO3 lattice to impurity ions. ESR investigations were performed which suggest probable lo calization of impurities incorporated by diffusion at Lit sites, impurities incorporated during growth at Ta5+ or interstitial sites and also strong s tructure deviations in Nd, Yb:LiTaO3 as compared to LiNbO3 single crystals. All single crystals under tests reveal good optical quality and higher abs orption than in the case of yttrium-aluminate garnets and lithium niobate w ith similar level of rare-earth concentration. (C) 2000 Elsevier Science S. A. All rights reserved.