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The polarized absorption, emission spectra and decay time measurements of Pr3+-doped CaYAlO4 single crystal have been performed at room temperature. Based on the Judd–Ofelt theory, the spectroscopic parameters $$\Upomega_{t} (t = 2,4,6)$$ , radiative transition probabilities, radiative lifetimes and branching ratios were obtained. The stimulated emission cross-section, fluorescence lifetimes and the quantum efficiency of the promising laser transition were also calculated and compared with other reported crystals. The results show that Pr3+:CaYAlO4 is a promising candidate for visible solid-state laser emission.

Thanks to diode pumping through an optical bifurcated fiber, we take benefit of the birefringence of the Yb3+-doped GdAl3(BO3)4 crystal to get two-polarization and two-wavelength laser operation both in CW and in passive Q-switch regimes. Typical differential slopes are 54% and 30% respectively for the o- and e-waves. In the pulse regime the two o- and e-pulses are synchronous but not simultaneous. Free running laser emissions near 1040 and 1046 nm for the e- and o-waves respectively were obtained with 2.5 nm FWHM.

From two positions of the concave output mirror of the laser cavity, diode-pumped ordinary or extraordinary polarization lasing of an Yb3+ -doped GdAl3(BO3)(4) nonlinear birefringent crystal is obtained. Translating the mirror at an intermediate position, simultaneous ordinary and extraordinary polarization lasing at 1046 (2.5 nm FWHM) and 1040 nm (2.2 nm FWHM), respectively, is obtained with up to 53% slope efficiency. Using a YAG:Cr4+ saturable absorber for passive Q-switching the cavity, ordinary and extraordinary pulses are obtained with an energy as high as 236 mu J and with about 30 ns duration. The two pulses of orthogonal polarizations can be separated by up to a few hundred ns, depending on the experimental conditions. The simultaneity of the pulses is observed but is difficult to maintain. A model constituted by two coupled equations reproduces reasonably well the experimental data. Repetition rates up to 3 kHz have been explored, corresponding to 4.65 W absorbed pump power.

NaGd(WO4)(2):Yb3+, Ho3+ single crystals have been grown by the Czochralski technique along the (0 0 1) orientation. Conversion of the infrared (IR) radiation at 980 nm into the visible emission in NaGd(WO4)(2) crystals containing several different concentrations of Yb3+ and Ho3+ has been investigated. The NaGd(WO4)(2): 8 at. % Yb3+, 4 at. % Ho3+ system exhibits intense red upconverted emission originating from the F-5(5) level. The upconversion mechanism in a Ho3+-Yb3+ system under near infrared excitation is discussed. It is concluded that the green emission is excited by energy transfers from Yb3+ to Ho3+, whereas excited state absorption is involved in the excitation of red emission. The emission cross-section of the F-5(5) -> I-5(8) transition at about 660 nm was estimated by using the Fuchtbauer-Ladengurg formula.

The polarized absorption and emission spectra of Pr3+ ions in NaY(MoO4)2 single crystal were investigated. The standard and modified Judd–Ofelt theory have been applied to the measured optical absorption intensities to determine the spectroscopic parameters, including the Judd–Oflet intensity parameters Ωt (t=2,4,6), the radiative transition rates, branching ratios, and emission cross-sections for various excited levels of Pr3+ ions. In samples with Pr3+ ions concentration of 2.00×1020 cm-3, the excitation of the 1D2 manifold decays non-radiatively by the electric dipole–dipole transfer between Pr3+ neighbors. The good spectroscopic properties show the possible application of the Pr3+ doped NaY(MoO4)2 crystal as a solid-state laser.

A Tm3+-doped NaLa(WO4)2 single crystal with a dimension of Φ20 mm×40 mm was grown by the Czochralski method. Anisotropic thermal expansion coefficients of this crystal were investigated. Polarized absorption spectra, emission spectra and decay curve were recorded at room temperature. The absorption and emission cross-section were presented. Based on the Judd–Ofelt analysis, we obtained the three intensity parameters: Ω2=10.21×10-20, Ω4=2.66×10-20, and Ω6=1.46×10-20 cm2. The radiative probabilities, radiative lifetimes, and branch ratios of Tm3+:NaLa(WO4)2 were calculated, too. Luminescence lifetime of the 3 H 4 level was measured to be 220 μs. The stimulated emission cross-section for the 3 F 4→3 H 6 transition were determined using the reciprocity method, potential laser gain for this transition were also investigated, the gain curves implied that the tunable range is up to 200 nm.

Yb3+:GdAl3(BO3)4 (hereafter Yb3+:GAB) crystals with large sizes and good optical quality have been grown by the top-seed solution growth (TSSG) method. The polarized absorption and emission spectra have been investigated at room temperature. For the σ-polarization, the intensities of both absorption and emission spectra are stronger than those for the π-polarization, the σ-absorption cross section of Yb3+ in GAB being 3.43×10-20 cm2 at 977 nm, and the σ-emission cross section being 0.98×10-20 cm2 at 1045 nm. The fluorescence lifetime of the 2 F 5/2→2 F 7/2 transition was measured to be 800 μs in the 5% doped sample used for our laser experiments, 993 μs in a 10% doped sample and 569 μs in a 0.5% doped sample. The laser parameters were estimated as: βmin=0.022, Isat=10.4 kW/cm2 and Imin=0.23 kW/cm2. About 0.4 W laseroutput at the wavelength of 1043 nm was achieved when the Yb3+:GAB crystal was pumped by a 974 nm laser diode, with 27.4% slope efficiency.

Thulium doped sodium gadolinium tungstate crystals with sizes of about 20 mm×45 mm were grown successfully by the Czochralski technique along the (001) orientation. X-ray powder diffraction (XRD) of sodium gadolinium tungstate was described and the linear thermal expansion coefficients for the c- and a-axes were measured as 1.60×10-5 and 7.89×10-6 °C-1. Polarized absorption spectra, and fluorescence spectra, as well as fluorescence decay curves of Tm3+-doped NaGd(WO4)2, have been recorded at room temperature and used to calculate the absorption and stimulated emission cross-sections. Based on the Judd–Ofelt theory, three intensity parameters were obtained. The luminescent quantum efficiency of the 3 H 4 level was determined to be approximately 65% for this material. The emission cross-section of the 3 F 4→3 H 6 IR transition at about 1.8 μm was estimated by the reciprocity method.