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Abstract Optical and spectroscopic properties of Er3+/Pr3+-codoped Gd 3 Ga 5 O 12 single-crystal grown by Czochralski method have been studied. Absorption spectrum of the crystal was measured at room temperature and Er3+ absorption cross-section spectral distributions were calibrated from it. The Er3+ spectroscopic properties were analyzed on the basis of the Judd-Ofelt theory. Fundamental spectroscopic parameters were obtained that include absorption coefficient, cross-section spectral distribution, electronic transition oscillator strength, Judd-Ofelt parameters, fluorescence branch ratio, transition probability, radiative and fluorescence lifetimes, and quantum efficiency as well. Study shows that Pr3+-codoping results in substantial change of Er3+ spectroscopic properties, in qualitative consistent with the previous fluorescence studying result. In addition, refractive index of the crystal was measured at different wavelengths using prism coupling method, and the Sellmeier equation reported previously for Er3+-only doped Gd 3 Ga 5 O 12 crystal is corrected. Highlights • Juud-Ofelt spectroscopic properties of Er3+/Pr3+:Gd 3 Ga 5 O 12 crystal were studied. • Pr codoping results in substantial increase of the Judd-Ofelt parameters. • Pr codoping induces shortening of Er3+ 2.7 and 1.5 μm lifetimes from ms to sub-ms. • The effect is related to two resonant energy transfers from Er3+ to Pr3+. • Different efficiencies of the two transfers enable to realize 2.7 μm lasing. [ABSTRACT FROM AUTHOR]

A series of singly Er 3+ -doped and doubly In 3+ /Er 3+ -doped congruent LiNbO 3 crystals were grown by Czochralski method. The Er 3+ -only doped crystals were grown from the growth melts doped with different concentrations of Er 2 O 3 up to 1 mol%, and the In 3+ /Er 3+ -codoped crystals from the melts doped with fixed 0.5 mol% Er 2 O 3 while varied In 2 O 3 contents of 0.0, 0.5, 1.0 and 1.5 mol%. The electro-optic coefficients γ 13 and γ 33 of these doped crystals were measured by Mach-Zehnder interferometry. Both clamped and unclamped coefficients were measured. The results show that both γ 13 and γ 33 reveal small Er 3+ and In 3+ doping effects. In the Er 3+ -only doping case, γ 13 almost does not change within the experimental error of 3%, γ 33 reveals a degradation tendency with a rise in Er 3+ doping level, but the degradation is no more than 5% in the considered Er 3+ concentration range 0–3.0 mol% (in crystal). In the In 3+ /Er 3+ -codoping case, both γ 13 and γ 33 can be regarded as unchanged in the studied In 3+ concentration range of 0–2.6 mol% (in crystal) within the error. The small Er 3+ or In 3+ doping effect is desired in light of electro-optic application of these crystals. It is qualitatively explained on the basis of EO coefficient model and doping effect on defect structure of LiNbO 3 . [ABSTRACT FROM AUTHOR]