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Fluorescence and absorption spectra at 530 nm (2H11/2→4I15/2), 560 nm (4S3/2→4I15/2), 660 nm (4F9/2→4I15/2), 980 nm (4I11/2→4I15/2), 1530 nm (4I13/2→4I15/2), and 2710 nm (4I11/2→4I13/2) of Er3+ in Gd3Ga5O12 single‐crystal codoped with Pr3+ have been measured. Judd‐Ofelt analysis yields the intensity parameters Ω2 = (0.68 ± 0.03) × 10−20 cm2, Ω4 = (0.60 ± 0.07) × 10−20 cm2, and Ω6 = (0.90 ± 0.17) × 10−20 cm2. A comparison with previously reported values of Er3+‐only doping case shows that Pr3+‐codoping causes slight change of both Ω2 and Ω4, while onefold increase of Ω6. From calculated radiative rates and measured fluorescence spectra, Er3+ emission cross‐section spectra were calibrated at first. Then, the absorption cross‐section spectra were calculated using McCumber relation. In parallel, the absorption cross‐section spectra were also obtained from the measured absorption spectrum, and compared with those obtained from the McCumber relation. The comparison shows that both methods give consistent result of absorption cross‐section spectrum. Further comparison with Er3+‐only doping case shows that Pr3+‐codoping causes considerable change of Er3+ cross‐section value. In spectrally mixing regions of Er3+ and Pr3+, Pr3+ emission affects little the determination of Er3+ emission cross‐section as Pr3+ fluorescence is much weaker than Er3+ fluorescence due to low Pr3+ concentration. [ABSTRACT FROM AUTHOR]

Congruent LiNbO3 crystals doped with 5.5/1, 6/0.15, and 7/0.8 mol %/mol % of Zn/Er were thermally treated at 1120 °C over 101 h using vapor transport equilibration (VTE) technique. Unpolarized visible and infrared absorption spectra of the VTE-treated and corresponding as-grown crystals were recorded at room temperature. It is shown that VTE treatment has brought these crystals closer to stoichiometric composition. X-ray powder diffraction and optical absorption results show that the VTE treatment induces the crystalline phase transformation with respect to Er3+ from the original Er3+:LiNbO3 to the ErNbO4 in all crystals studied. The formation of the ErNbO4 phase results in substantial absorption changes that include the drop of the transparency in the visible region, the reduction of Er3+ absorption, and the Zn-doping-level-dependent changes in spectral shape and peaking position at 0.98 and 1.5 μm regions. Based upon the measured absorption spectra, the influences of Zn-doping level and VTE treatment on the Er3+ spectroscopic properties were studied by using the Judd-Ofelt (JO) theory. The results show that the VTE treatment has a little effect on the fluorescence branch ratio, while a large effect on the JO parameters, oscillator strength, and electron transition probability. The Zn doping level affects the JO parameters, oscillator strength, and transition probabilities of some individual manifolds. In addition, the VTE treatment leads to the increases of the theoretical radiative lifetimes of almost all manifolds considered. For the emission at 1.5 μm, the lifetime increase is as much as 30% and the theoretical results are in well agreement with the experimental data. The VTE-induced lifetime increase is qualitatively explained. [ABSTRACT FROM AUTHOR]