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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]

We measured fluorescence spectra of visible and infrared electronic transitions at 530 (2H 11/2 → 4I 15/2), 560 (4S 3/2 → 4I 15/2), 670 (4F 9/2 → 4I 15/2), 980 (4I 11/2 → 4I 15/2), 1530 (4I 13/2 → 4I 15/2) and 2700 nm (4I 11/2 → 4I 13/2) of Er3+ in Gd 3 (Al 0.4 Ga 0.6) 5 O 12 garnet single-crystal excited at the wavelength 520 nm (for the 980 nm emission) or 980 nm (for other emissions). From measured fluorescence spectrum, Er3+ emission cross-section spectrum was calibrated for each transition. Absorption cross-section spectra were further derived on the basis of McCumber equation, and compared with those spectra obtained from measured absorption spectrum on the basis of the Beer-Lambert law. The comparison showed that the results given by two methods can be regarded as same within the error. The transient features of visible and infrared emissions were also studied under pulse excitation. The results showed that, while the three IR emissions at 980, 1530 and 2700 nm all follow a mono-exponential function, both green and red 980-nm-upconverted emissions at 560 and 670 nm exhibit non-mono-exponentially decaying feature, and each decaying trace can be fitted by a sum of two exponential functions. The non-mono-exponential feature is related to cross relaxation caused by non-radiative short-distance energy transfer between clustered Er3+ sites. • Cross-section spectra of Er3+ ions in Gd 3 (Al,Ga) 5 O 12 garnet crystal were studied. • Emission cross-section spectra are computed from measured fluorescence spectra. • Absorption cross-section spectra are derived by two ways and results are same. • 980-nm-upconverted visible emissions show non-mono-exponential transient feature. • It is caused by non-radiative energy transfer between clustered Er3+ sites. [ABSTRACT FROM AUTHOR]

A previous paper [J. Lumin. 177 (2016) 219] has studied Judd-Ofelt spectroscopic properties of Er3+ (0.5 at%)-doped Gd 3 (Al, Ga) 5 O 12 garnet single-crystal, and reported the Judd-Ofelt intensity parameters Ω 2 = 1.47 × 10−20 cm2, Ω 4 = 1.38 × 10−20 cm2 and Ω 6 = 1.19 × 10−20 cm2. We have performed a re-study on the Judd-Ofelt spectroscopic properties of a similar garnet single-crystal Er3+(20 at%)-doped Gd 3 (Al 0.4 Ga 0.6) 5 O 12 , and obtained quite different values of Judd-Ofelt intensity parameters Ω 2 = (0.34 ± 0.11) × 10−20 cm2, Ω 4 = (0.48 ± 0.16) × 10−20 cm2 and Ω 6 = (1.05 ± 0.17) × 10−20 cm2. The quite different Ω t values given by two studies are mainly due to remarkably different absorption characteristics of Er3+ in the crystals employed in two studies, and factors that lead to quite different absorption characteristics are discussed. Another reason is that the hypersensitive transition at 380 nm was excluded from the Judd-Ofelt calculation in that paper, resulting in deviation of their result. Instead, all of the Er3+ absorption bands were included in our calculation, allowing to obtain more accurate Ω t values. Quite different Ω t values lead to considerable differences of relevant spectroscopic parameters, such as radiative rates and lifetimes of typical Er3+ emissions, for which the difference from each other is as much as three times. In addition, visible, near-infrared and mid-infrared fluorescence spectra and lifetimes of Er3+ in the studied crystal were measured, and the emission characteristics are discussed. • Er:Gd 3 (Al,Ga) 5 O 12 crystal was grown and its spectroscopic properties are studied. • Judd-Ofelt analysis was done and the result is compared with previously reported. • The Judd-Ofelt data obtained show large differences from the previously reported. • Main reason is large difference of Er3+ absorption features in two studies. • Sellmeier equation, lattice constant and segregation coefficient are presented. [ABSTRACT FROM AUTHOR]