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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]

Abstract: We have measured OH absorption spectra of a 0.47-mm-thick Z-cut MgO (5mol% in melt):LiNbO3 crystal subjected to post-growth Li-poor vapor transport equilibration (VTE) treatments at 1100°C for different durations ranging from zero to 395h. These spectra allow the evolution of OH absorption characteristics with prolonged VTE to be followed. After 2h of VTE process an additional absorption appears at 3483cm−1. A transition regime that the original 3536cm−1 and new 3483cm−1 absorptions simultaneously appear exists within the VTE duration range of 2–16h. In this regime, the 3536cm−1 absorption becomes weak gradually and eventually disappears around 16h while the 3483cm−1 absorption increases remarkably with the prolonged VTE. The presence of transition regime gives a hint that the 3483cm−1 absorption is due to the VTE-induced formation of a new center. Based upon the spectral features, we have suggested a simple three-layer (two on surface and one in the center of crystal plate) model to describe the depth profile of the photorefractive damage MgO concentration threshold in the crystal in the transition regime. A Li out-diffusion theory is suggested and correlated with the model. To support the Li out-diffusion theory, some additional experiments have been done. These include the depth profile characterization of VTE-induced Li2O content reduction and the measurement of the surface Li2O content as a function of the VTE duration. A quantitative analysis and discussion shows that the model is well supported by the experimental results. [Copyright &y& Elsevier]

Abstract: The emission and absorption spectra of Er3+ ions in Er2O3 powder are investigated at room temperature. The crystal field splitting of 4I15/2, 4I13/2, 4I9/2 and 4S3/2 multiplets of Er3+ was calculated using a parameterized Hamiltonian including crystal field terms. A final standard deviation of 5.3cm−1 is obtained between 22 calculated and experimental Stark. The strength crystal field parameters of Er2O3 powder are compared to those of erbium doped Y2O3 single crystal. In addition, the location of the ground and the first excited states of Er3+ in Er2O3 powder is determined. The 4I15/2 ground state of Er3+ is located at 12750cm−1 below the valence band edge. The 4I13/2 and 4I11/2 multiplets are set in resonance with the valence band. A configuration coordinate diagram is proposed for Er3+ in Er2O3 powder. [Copyright &y& Elsevier]

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]

In the previous paper "Optical and Judd‐Ofelt spectroscopic study of Er3+‐doped strontium gadolinium gallium garnet single‐crystal" (J Am Ceram Soc. 2019;102:873–878), we have reported optical and Judd‐Ofelt spectroscopic properties of Er3+‐doped strontium gadolinium gallate (SrGdGa3O7) single‐crystal, and the Judd‐Ofelt study was performed on the basis of unpolarized absorption spectrum of the crystal. Present work reports the corrected unpolarized absorption spectrum and Er3+ concentration in the crystal, and hence corrected Judd‐Ofelt spectroscopic properties and cross‐section data. In addition, the polarization effect was considered in the Judd‐Ofelt analysis on the basis of polarization‐resolved absorption spectra. Effective Judd‐Ofelt parameters are presented and discussed in comparison with the results from the unpolarized spectrum, and consistent results have been obtained. This study also considers the effects of some other factors on the Judd‐Ofelt parameters. These include Er3+ concentration and selection of Er3+ absorption bands for the Judd‐Ofelt analysis. [ABSTRACT FROM AUTHOR]

Abstract Visible and infrared absorption and emission spectra of Er3+-doped strontium gadolinium gallate (SrGdGa 3 O 7) single-crystal were measured at room temperature. From the measured fluorescence spectra, the Er3+ emission cross section spectra were calculated at first. Then, by utilizing McCumber relation, the absorption cross section spectra were further calculated. In parallel, the absorption cross section spectra were also calculated from the measured absorption spectra of the crystal, and compared with those spectra calculated from the McCumber relation. The comparison shows that the absorption cross section spectra obtained using the McCumber relation are in reasonable agreement with those deduced from the measured absorption spectrum. Graphical abstract Visible, near-infrared, and mid-infrared emission and absorption cross section spectra of Er3+ in SrGdGa 3 O 7 single-crystal have been calibrated from measured fluorescence spectra using the McCumber theory. The absorption cross-section spectrum was also calibrated from the measured absorption spectrum. Comparison shows that the absorption cross section spectra calibrated from the McCumber theory are reasonably consistent with those from the absorption spectrum. Present work presents complete cross section knowledge of the studied crystal. fx1 [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]

Judd-Ofelt analysis was done for Er3+-doped NaLa(WO 4) 2 µm-sized phosphor using a method based on measured diffuse reflection spectrum and Er3+ 1.5 μm fluorescence lifetime. Judd-Ofelt intensity parameters, radiative rate, fluorescent branch ratio and radiative lifetime of some transitions of Er3+ ions in the phosphor have been obtained. • Er3+-doped NaLa(WO 4) 2 phosphor was synthesized by solid-state chemical reaction. • Its diffuse reflection spectrum and Er3+ 1.5 μm emission lifetime were measured. • Judd-Ofelt analysis was done on the basis of the measured spectrum and lifetime. • Radiative rate, fluorescent branch ratio and radiative lifetime were obtained. • The phosphor is promising for use in ratiometric fluorescence thermometry. Er3+-doped NaLa(WO 4) 2 is a promising phosphor material for applications in many fields including the ratiometric thermometry based on thermal effect of fluorescence intensity ratio (FIR) of green fluorescence of Er3+, which is directly correlated with Judd-Ofelt parameters Ω i (i = 2, 4, 6). Present paper reports synthesis and Judd-Ofelt spectroscopic properties of Er3+-doped NaLa(WO 4) 2 µm-sized phosphor. The phosphor was synthesized by solid-state chemical reaction and characterized by X-ray diffraction and Raman scattering techniques. The results show that the phosphor is dominated by NaLa(WO 4) 2 crystalline phase and has a maximum phonon energy 927 cm−1. Judd-Ofelt analysis was done for the phosphor using a safe, reliable method based on diffuse reflection spectrum and Er3+ 1.5 μm fluorescence lifetime. First, diffuse reflection spectrum of the phosphor was measured and relative absorption spectrum was calibrated from it using Kubelka-Munk theory. Second, Er3+ 1.5 μm fluorescence lifetime of the phosphor was measured and absorption cross-section spectrum was obtained based on the assumption that the 1.5 μm emission has 100% quantum efficiency. Finally, based on the absorption cross-section spectrum, standard Judd-Ofelt analysis was carried out to extract the Ω i. Radiative rate, fluorescent branch ratio and radiative lifetime of some transitions have been obtained from the known Ω i values. In addition, FIR proportional factor was evaluated in terms of Ω i and compared with those values of other materials. The result shows that the phosphor has a better prospect for the application in ratiometric thermometry. [ABSTRACT FROM AUTHOR]

Validity of Judd-Ofelt spectroscopy based on measured diffuse reflectance spectrum and fluorescence lifetime of a purely radiative electronic transition of rare-earth-ion in a powder material has been demonstrated. Two representative powder samples of Er3+-doped LiNbO 3 and Er3+/Yb3+-codoped NaYF 4 , which have considerably different phonon energies, 880 and 380 cm−1, respectively, have been exemplified to demonstrate the validity. First, diffuse reflectance spectrum was measured for each powder sample and relative absorption spectrum was calibrated from it using Kubelka-Munk relation. Second, fluorescence lifetime of purely radiative 1.5 μm emission of Er3+ was measured and absolute absorption cross-section spectrum was calibrated on the basis of the assumption that the measured 1.5 μm fluorescence lifetime equals the radiative lifetime. Finally, the Judd-Ofelt parameters Ω t (t = 2, 4, 6) are calculated on the basis of the absolute absorption cross-section spectrum. For comparison, Judd-Ofelt analysis was also performed on the Er3+-doped LiNbO 3 single-crystal on the basis of the absorption spectrum obtained from Beer-Lambert law. The Ω t result of Er3+-doped LiNbO 3 powder sample is compared with that of single-crystal state. The comparison shows that the Ω t result of the powder sample can be considered as the same as that of the single-crystal state within the error, confirming the validity of the method. The study on the Er3+/Yb3+-codoped NaYF 4 microcrystal powder allows us to reach the same conclusion. • A method for Judd-Ofelt (J-O) analysis of a phosphor material is validated. • The method is based on diffuse reflectance spectrum and fluorescence lifetime. • It is validated by comparing J-O results of Er:LiNbO 3 powder and single crystal. • And by comparing the results of Er/Yb:NaYF 4 powder with those reported earlier. • Results of powder and single-crystal states are same, validating thus the method. [ABSTRACT FROM AUTHOR]

In the previous paper [J. Alloys Compd. 102 (2019) 873–878], optical and Judd-Ofelt (J-O) spectroscopic properties of Er3+/Pr3+-codoped Gd 3 Ga 5 O 12 single-crystal have been reported and the J-O study was performed on the basis of measured absorption spectrum of the crystal. Present paper reports corrected absorption spectrum and J-O spectroscopic parameters of the crystal, which include J-O intensity parameters, oscillator strengths, fluorescence branch ratios, radiative rates and radiative lifetimes. Comparison shows that the previous paper erroneously reported almost one order of magnitude larger absorption cross-section, J-O intensity parameters, oscillator strength and radiative rate as well. A further comparison with previously reported results of Er3+-only doped crystal reveals that the Pr3+-codoping causes considerable spectroscopic change in absorption cross-section, J-O intensity parameters, oscillator strength and radiative rate of Er3+ transitions, and the reason of the change is discussed from the viewpoint of Pr3+-codoping and crystal growth procedure effect on ion environment of Er3+. In addition, errors are given for both the J-O parameters and radiative probabilities of several typical Er3+ emissions. [ABSTRACT FROM AUTHOR]