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A promising 2.9 µm Ho:GdYTaO4 laser crystal was grown successfully by the Czochralski method for the first time. The crystal belongs to the monoclinic space group of I2/a (No. 15) and high crystalline quality is demonstrated by X-ray rocking curves. The spectral properties of Ho:GdYTaO4 crystal at room temperature are investigated. Based on the Judd–Ofelt theory, the intensity parameters, spontaneous transition probabilities, fluorescence branching ratios, and radiative lifetimes are obtained in detail. The strongest emission peak is located at 2848 nm, and the full width at half maximum is about 15 nm. The experimental lifetimes of 5I6 and 5I7 levels are 0.31 and 8.08 ms, respectively. Moreover, the Stark levels of 5I6, 5I7, and 5I8 are identified and the splitting values are calculated to be 254.1, 226.7, and 370. 4 cm−1, respectively.

30 at% Er3+:GSAG single crystal was successfully grown by the Czochralski method. The dislocation of (111) face is studied using the chemical etching with the phosphoric acid etchant. The luminescence properties at 2.6–3.0 µm are systematically studied by measuring the fluorescence spectra and lifetimes to the transition of 4I11/2 → 4I13/2. The long fluorescence lifetime, high fluorescence intensity, and large gain σem spectra indicate that the 30 at% Er:GSAG crystal has the great potential for the multi-wavelength laser output at 2.6–3.0 µm. Meanwhile, the absorption and fluorescence properties of 30 at% Er:GSAG crystal under the gamma-ray radiation with three different intensities (35, 70, and 105 Mrad) have been investigated, indicate that this crystal can be considered as a promising MIR laser gain medium for being used under radiant environment. In addition, the luminescence property of 30 at% Er:GSAG crystal in visible and 1.5–1.7 µm was also studied, which shows the possibility to generate the laser around 1.6 µm.

Er3+ doped GSAG laser crystal with high optical quality was grown successfully by the Czochralski method for the first time. The structural parameters and the high crystalline quality of this crystal were determined. Judd-ofelt (J-O) parameterization scheme was applied to analyze the absorption spectra at room temperature. Accordingly, the lines strengths, oscillator strengths, transition probabilities, fluorescence branching ratios, and radiative lifetimes were calculated to characterize the laser properties of Er:GSAG crystal. Additionally, the fluorescence spectra and lifetimes of Er:GSAG crystal were measured and studied. The stimulated emission cross-section spectra and gain cross-section spectra were evaluated for 4I13/2 →4I15/2 (1.5–1.6 µm) transitions which indicate high potential of 1 at% Er:GSAG for laser emissions at 1567 and 1605 nm. Furthermore, the possibility of Er:GSAG crystal to realize the visible laser output pumped by the GaN LDs were initially studied and analyzed.

1 at% Er 3+ doped Er: GdTaO 4 laser crystal with high optical quality was successfully grown by the Czochralski method. The structural parameters were obtained by the X-ray Rietveld refinement. A high crystalline quality of Er: GdTaO 4 was determined by the X-ray rocking curve. The transition intensity parameters of Er 3+ ions were fitted according to the absorption spectra along three principal polarization directions. The relatively larger emission cross section (1.022×10 −20 cm 2 ), long fluorescence lifetime ( 5.66 ms) and relatively weaker reabsorption phenomenon around 1.6 µm indicate that 1 at% Er: GdTaO 4 crystal can be used as a promising NIR laser material. Meanwhile, the stimulated emission cross-section spectra along three principal polarization directions were investigated for 4 I 13/2 → 4 I 15/2 transitions at 1.5–1.6 µm which indicates a great potential of Er: GdTaO 4 for multi-wavelength emission at 1.5–1.6 µm. In addition, the possibility of generating green and red lasers in Er: GdTaO 4 was also analyzed and evaluated.

Recently, we proposed GdTaO4 as a promising high-density scintillator but the scintillation mechanism was still unknown. In this paper, we investigated the temperature-dependent luminescent properties of GdTaO4 crystal. The emission spectra are characterized by a broad band composed of two Gaussian components located at ~2.2 eV and ~2.7 eV of 8–300 K, which are both thermally quenched with the activation energy of 156 meV and 175 meV, respectively. These two bands are believed to be from different luminescent centers, judging from the excitation spectra, thermal activation energy and decay curves. Additionally, it was also found that the annealing atmosphere exerts little influence on the luminescence intensity. Based on the results, we tentatively assigned the high-energy band to self-trapped excitons (STE) localized in TaO 4 3 − groups and the low-energy band to relaxed excitons related to lattice imperfections.