Temperature-Dependent and Threshold Behavior of Sm(3+) Ions on Fluorescence Properties of Lithium Niobate Single Crystals

Temperature-dependent and threshold behavior of Sm(3+) ions on fluorescence properties of lithium niobate (LiNbO(3), LN) single crystals were systematically investigated. The test materials, congruent LiNbO(3) single crystals (Sm:LN), with various concentrations of doped Sm(3+) ions from 0.2 to 2.0 mol.%, were grown using the Czochralski technique. Absorption spectra were obtained at room temperature, and photoluminescence spectra were measured at various temperatures in the range from 73 K to 423 K. Judd–Ofelt theory was applied to calculate the intensity parameters Ω(t) (t = 2, 4, 6) for 1.0 mol.% Sm(3+)-doped LiNbO(3), as well as the radiative transition rate, A(r), branching ratio, β, and radiative lifetime, τ(r), of the fluorescent (4)G(5/2) level. Under 409 nm laser excitation, the photoluminescence spectra of the visible fluorescence of Sm(3+) mainly contains 568, 610, and 651 nm emission spectra, corresponding to the energy level transitions of (4)G(5/2)→(6)H(5/2), (4)G(5/2)→(6)H(7/2), and (4)G(5/2)→(6)H(9/2), respectively. The concentration of Sm(3+) ions has great impact on the fluorescence intensity. The luminescence intensity of Sm (1.0 mol.%):LN is about ten times as against Sm (0.2 mol.%):LN at 610 nm. The intensity of the fluorescence spectra were found to be highly depend on temperature, as well as the concentration of Sm(3+) ions in LiNbO(3) single crystals, as predicted; however, the lifetime changed little with the temperature, indicating that the temperature has little effect on it, in Sm:LN single crystals. Sm:LN single crystals, with orange-red emission spectra, can be used as the active material in new light sources, fluorescent display devices, UV-sensors, and visible lasers.