Alexander V. Malov

Intensities of hypersensitive transitions in garnet crystals doped with Er3+ ions

We examine the oscillator strengths and the intensity parameters Ωt (t = 2, 4, 6) of yttrium-aluminum, scandium-containing, and gallium garnet crystals doped with Er3+ ions. A comparative analysis of the oscillator strengths and the intensity parameters Ωt (t = 2, 4, 6) of garnets with different contents of Al3+ and Sc3+ ions (Gd2.4Er0.5Sc1.8Al3.3O12, Gd2.4Er0.5Sc1.9Al3.2O12, Gd2.4Er0.5Sc2.0Al3.1O12) is performed, as a result of which the oscillator strengths and the intensity parameters Ωt (t = 2, 4, 6) of these crystals are shown to have close values. We find that Ca3(NbGa)5O12 crystals doped with Er3+ ions are characterized by highest values of the oscillator strengths for hypersensitive transitions and of the intensity parameter Ω2 of Er3+ ions compared to the values of these quantities in the examined garnet crystals, which is determined by the fact that the symmetry of the local environment of Er3+ ions in these crystals is C1, C2, or C2ν. We reveal that, as the concentration of Er3+ ions in these crystals increases from 1 to 39 at %, both the oscillator strength of the hypersensitive transition 4I15/2 → 2H11/2 of Er3+ ions and their intensity parameter Ω2 tend to decrease, which can be related to an increase in the relative fraction of Er3+ ions with higher symmetry of the local environment.

Intensity parameters for Er3+ ions in calcium-niobium-gallium garnet crystals

Based on the analysis of the absorption spectra of Er-doped calcium-niobium-gallium garnet (Er:CNGG) crystals according to the Judd-Ofelt theory, the intensity parameters for these crystals are determined to be Θ2 = 3.43 × 10−20 cm2 Θ4 = 1.20 × 10−20 cm2, and Θ6 = 0.58 × 10−20 cm2. The parameters found are compared with the intensity parameters for other laser oxide crystals. Using these intensity parameters, the probabilities of radiative transitions between the energy levels of Er3+ ions in CNGG crystals and the luminescence branching ratios βJJ’ are calculated. From the measured lifetime of the 4I11/2 level of Er3+ ions (τ = 626 μs) and the probability of the radiative transition from this level (A = 192 s−1), it is found that about 88% of the excitation energy in the Er:CNGG crystals is nonradiatively transferred from the 4I11/2 to the 4I13/2 level. It is suggested that an increase in the oscillator strength and in the line strength of the 4I15/2 → 2H11/2 transition of Er3+ in CNGG crystals, as well as an increase in the intensity parameter Θ2 with respect to the corresponding parameters for other garnet crystals are caused by the existence in CNGG crystals of Er3+ centers with the environment symmetry lower than D2.

Structure and spectral-luminescence properties of yttrium-stabilized zirconia crystals activated with Tm3+ ions

Yttrium-stabilized zirconia crystals (ZrO2-13.8 mol % Y2O3-0.2 mol % Tm2O3 and ZrO2-12 mol % Y2O3-2 mol % Tm2O3) have been grown by directed crystallization from a melt in a cold container using direct high-frequency melting. The crystals have been analyzed by X-ray diffraction. The spectral-luminescence properties have been studied, and the cross-relaxation efficiency for Tm3+ ions (3H4 → 3F4, 3H6 → 3F4) in these crystals has been estimated.

The study of spectroscopic and luminescence properties of disordered laser crystals calcium niobium gallium garnet doped with Er3

The results of spectroscopy of disordered Er-doped calcium-niobium- gallium garnets (CNGG: Er) are displayed. Based on the Judd-Ofelt theory, three intensity parameters Ωt (t=2, 4, 6) for Er ions concentration from 6 at. % in these crystals were obtained. The oscillator strength for hypersensitivity transition 4I15/2→2H11/2 and intensity parameter Ω2 of Er3+ ions in CNGG: Er crystals are higher than corresponding values for other Er-doped garnets. These results we explain by the presence in these crystals of optical centers Er with the environment symmetry lower than D2. Gain crosssection for laser transition 4I13/2 → 4I15/2 of Er3+ ions was obtained using absorption and emission cross-data for transition 4I15/2 → 4I13/2 and 4I13/2 → 4I15/2 respectively.