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The polarized absorption and emission spectra have been measured for the Tm3+ doped NaY(MoO4)2 crystal and spectral parameters have been estimated from the absorption data based on the Judd–Ofelt theory. The effective intensity parameters Ω t eff (t = 2, 4, 6) are 11.67 ×10−20, 2.21 × 10−20, 1.74 × 10−20 cm2, respectively. From the intensity parameters, the radiative transition probabilities, radiative lifetimes, branching ratios and the emission cross-section have been calculated. In comparison with other Tm3+ doped laser crystals, Tm3+:NaY(MoO4)2 crystal has potential as a promising laser crystal.

The single crystal of ZnWO 4 :Ho 3+ was grown by Czochralski technique. The XRD, absorption spectra, fluorescence spectrum are presented, and the Judd–Ofelt (J–O) intensity parameters Ω 2 , Ω 4 , Ω 6 are obtained to be 4.61 × 10 −20 cm 2 , 0.16 × 10 −20 cm 2 , 0.48 × 10 −20 cm 2 , respectively. Calculated radiative transition rate, branching ratios, and radiative lifetime for different transition levels of ZnWO 4 :Ho 3+ crystals are presented. The most intense line correlative with the transition 5 S 2 → 5 I 8 at 543 nm is potentially used for green solid state laser, and the fluorescence lifetime of this energy level is 14.1 μs.

Good quality crystals ZnWO4 activated with Er3+ have been grown by means of Czochralski method and characterized using optical spectroscopy techniques. XRD, absorption spectra, fluorescence spectrum are presented and the Judd-Ofelt intensity parameters 522, 524, and 526 are obtained to be 6.76 x 10(-20), 0.37 x 10(-20), and 0.50 x 10(-20) cm(2), respectively. Along crystallographic axes, refractive indices are presented. The fluorescence decay time of the I-4(3/2) level has also been investigated and shows an exponential behavior with a lifetime value of 5.52 ms. The crystal is potentially used for green and infrared eye-safe lasers. (c) 2006 Elsevier B.V. All rights reserved.

Dy3+-doped NaGd(WO4)(2) crystal with sizes of about Phi 20x40 mm(2) was grown by the Czochralski technique along the (001) orientation. Polarized absorption spectra, fluorescence spectra, and fluorescence decay curve of Dy3+-doped NaGd(WO4)(2) have been recorded at room temperature. Based on the Judd-Ofelt (J-O) theory, the intensity parameters from the measured line strengths were evaluated. The J-O parameters were used to predict radiative transition probabilities, radiative lifetimes and branching ratios for various excited levels of Dy3+-doped NaGd(WO4)(2) crystal. The luminescent quantum efficiency of the F-4(9/2) level was determined to be approximately 63% for this material. The emission cross-section of the F-4(9/2)-> H-6(13/2) transition was estimated by using the Fuchtbauer-Ladengurg method. (c) 2006 Elsevier B.V. All rights reserved.

The Dy3+-doped NaY(MoO4)2 single crystals were grown successfully by the Czochralski technique. The main spectroscopic properties (absorption, luminescence, decay curve) of Dy3+-doped NaY(MoO4)(2) have been determined for both the sigma and pi polarizations. By using the Judd-Ofelt theory, the measured room temperature absorption spectra were applied to determine the intensity parameters, spontaneous transition probabilities, branching ratios, and radiative lifetimes of Dy3+ transitions. The results show that the Dy3+-doped Nay(MoO4)(2) crystal may realize the yellow laser operation. (C) 2006 Elsevier B.V. All rights reserved.

Single-crystal ZnWO4:Dy3+ was grown by Czochralski technique. The XRD, absorption spectra as well as fluorescence spectrum are investigated and the Judd-Ofelt intensity parameters Omega(2), Omega(4), Omega(6) are obtained to be 7.76 x 10(-20) cm(2), 0.57 x 10(-20) cm(2), 0.31 x 10(-20) cm(2), respectively. Calculated radiative transition rate, branching ratios and radiative lifetime for different transition levels of ZnWO4:Dy3+ crystals are presented. Fluorescence lifetime of F-4(9/2) level is 158 mu s and quantum efficiency is 66%. The most intense fluorescence line at 575 nm correlative with transition F-4(9/2) -> H-6(13/2) is potentially for application of yellow lasers. (c) 2006 Elsevier B.V. All rights reserved.

Nd3+-doped NaLa(WO4)(2) single crystal with a dimension of circle divide 20 mm x 40 mm and a good optical quality was grown by Czochralski method. The polarized absorption spectra and emission spectra were measured at room temperature. The absorption cross-section and emission cross-section were presented. The Judd-Ofelt theory, extended to anisotropic system, has been applied to evaluate the intensity parameters Omega(t) (t = 2,4,6), radiative transition rates A, radiative lifetimes tau(R) and fluorescent branching ratios beta. The calculated radiative lifetime was compared with the experiment data for the F-4(3/2) emitting level. All spectral features are strongly affected by an inhomogeneous broadening connected with the 'disordered crystal' character of the title compound. (c) 2006 Elsevier B.V. All rights reserved.

Holmium doped sodium gadolinium tungstate crystals with sizes of about 020 mm x 40 mm were grown successfully by the Czochralski technique along the (001) orientation. Polarized absorption spectra, fluorescence spectra and fluorescence decay curve of Ho3+-doped NaGd(WO4)(2) have been recorded at room temperature. Based on the Judd-Ofelt theory, three intensity parameters were obtained. The spectroscopic parameters of this crystal such as the oscillator strengths, radiative transition probabilities, radiative lifetimes as well as the branching ratios were calculated. The fluorescence lifetime tau(f) of the S-5(2) level was measured to be 5 mu s. (c) 2006 Elsevier B.V. All rights reserved.

Tin doped NaBi(WO4)(2) of good optical quality with sizes of about 20 min x 20 mm x 40 mm was grown successfully by the Czochralski technique. The absorption spectra for both sigma- and pi-polarizations were recorded at room temperature. Based upon these data, the oscillator strengths and radiative transition rates were evaluated. The sigma- and pi-polarized emission spectra together with the fluorescence decay curve were also obtained. The emission cross-section of the potential laser transition at 1460 nm was determined to be 1.49 x 10(-19) cm(2). The results show that Tm3+:NaBi(WO4)(2) crystal is a promising laser material. (c) 2006 Elsevier B.V. All rights reserved.

The polarized absorption, emission spectra and the fluorescence decay curve of Er3+ ions in the anisotropic NaY(MoO4)2 crystal were investigated at room temperature, and spectral parameters have been calculated from the absorption data based on the Judd–Ofelt theory. The experimental oscillator strengths for the transitions from the ground state to excited states were compared with the theoretical oscillator strengths calculated from the Judd–Ofelt theory. The emission cross-section and gain cross-section for the π- and σ-spectrum were determined for the 4H13/2 → 4H15/2 transition of special interest for laser application.

Tm 3 + : Ba 3 Gd 2 ( BO 3 ) 4 crystal with the size up to Φ 13 mm×44 mm was grown successfully by the Czochralski technique and its optical properties were presented. The absorption cross-section and emission cross-section were presented. Also, the potential laser gain near 1.9 μm was investigated. In the framework of the Judd–Ofelt (J–O) theory, the intensity parameters were calculated to be: Ω2=11.375×10−20 cm2, Ω4=5.077×10−20 cm2 and Ω6=6.524×10−20 cm2. The spectroscopic parameters of this crystal such as the oscillator strengths, radiative transition probabilities, radiative lifetime as well as the branching ratios were calculated, too. This crystal is promising as a tunable infrared laser crystal.

A systematic investigation of room temperature absorption and emission spectra were presented for trivalent holmium in a crystal of NaY(MoO4)2. Oscillator strengths of the transitions to all levels up to 361 nm were calculated from the absorption spectra. Judd–Ofelt intensity parameters of Ho3+ were used to calculate the radiative transition rates, branching ratios and radiative lifetimes. The emission cross-sections for the 5S2 → 5I8 and 5I7 → 5I8 transitions of special interest for laser application were determined.

Ca3Gd2(BO3)4:Nd3+ crystals of high optical quality with a size up to 20 × 50 mm were grown by the Czochralski method. The absorption spectra of the crystal in three mutually perpendicular arbitrary directions were measured. Based on Judd–Ofelt and TPM methods, the intensity parameters Ω t (t = 2, 4, 6), the experimental and theoretical oscillator strengths, the radiative transition rates, radiative lifetime and fluorescent branching ratios of Nd3+ from 4F3/2 to 4IJ, were obtained. The fluorescence spectrum and decay curve under excitation at 808 nm were also measured. The stimulated emission cross-section and radiative quantum efficiency were also calculated.

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.

Ca3(BO3)2 single crystals have been grown by the Czochraski technique. The absorption and emission spectra have been measured at room temperature. From the Judd–Ofelt theory analysis, the intensity parameters were determined to be Ω2 = 4.63 × 10–20 cm2, Ω4 = 2.40 × 10–20 cm2, and Ω6 = 10.4 × 10–20 cm2. The calculated radiative probabilities, radiative lifetimes, and the branching ratios have been evaluated for the 4F3/2 excited state using the calculated intensity parameters. The stimulated emission cross-section was also measured at 1060 nm. The results indicate that this crystal can be considered as a promising material for solid-state laser application. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper reports the growth of Nd3+:NY(WO4)2 crystal with high optical quality and large size. Nd3+:NY(WO4)2 crystal with the dimension Φ30×75 mm2 and optical homogeneity 4×10−5 was grown by Czhchoralski method: the seed used was [1 0 0] orientation, the pulling rate and rotating rate were 0.5–1.25 mm/h and 15 rpm, respectively. The growing processes and characteristics of Nd3+:NY(WO4)2 crystal was discussed. Its unpolarized absorption spectra and emission spectra were measured. The absorption cross-section and emission cross-section were presented. Based on the Judd–Ofelt theory, we obtained the three intensity parameters: Ω 2 = 5.8 × 1 0 - 20 , Ω 4 = 5.74 × 1 0 - 20 , and Ω 6 = 4.32 × 1 0 - 20 cm 2 . The radiative probabilities, radiative lifetimes, branch ratios and quantum efficiency of Nd3+:NY(WO4)2 were calculated too.

Dy 3+ : Ca 3 (BO 3 ) 2 crystal was grown successfully by the Czochraski technique. The absorption spectrum was measured and its absorption peaks were assigned. The Judd–Ofelt intensity parameters were found to be Ω 2 =5.216×10 −20 , Ω 4 =1.858×10 −20 , Ω 6 =0.623×10 −20 cm 2 . The spectroscopic parameters of this crystal such as the oscillator strengths, radiative transition probabilities, radiative lifetime as well as the branching ratios were calculated. Also, room temperature luminescence decay curve in correspondence with the emission line 4 F 9/2 → 6 H 13/2 centered at 575 nm was measured.

Large novel birefringent pure and rare earth-doped calcium borate crystals (Ca 3 (BO 3 ) 2 ) have been grown successfully by Czochralski technique. Thermal expansion coefficients of pure Ca 3 (BO 3 ) 2 have been obtained for the first time. Trivalent rare earth ions (RE 3+ ), such as Dy 3+ - and Nd 3+ -doped calcium borate crystal, have been grown for optic application. Absorption and fluorescence spectra as well as fluorescence decay curves of Dy 3+ -, Nd 3+ -doped Ca 3 (BO 3 ) 2 crystals are measured at room temperature. Optical spectra show that there are obvious absorptions at ultraviolet to IR region. The strong emissions in visible and infrared region show that calcium borate is a suitable for rare earth-doped laser crystal.

The crystal of ZnWO4 doped with Co2+ has been grown by the Czochralski technique. The orientation procedure was presented. Along the crystallographic axes, the principal coefficients of thermal expansion and absorption spectra were measured and discussed. Based on the data, the crystal field parameter 10Dq, Racah parameter B, as well as the absorption cross sections were calculated. The nonlinear dependence of optical absorption on concentration of cobalt ions was found and discussed in single crystal Co2+:ZnWO4. The results indicate that inner defects such as natural cleavage or slip faces in crystal are important in the study of optical and thermal properties.

Er3+:SrWO4 crystal of good optical quality was grown by Czochralski technique method. Polarized absorption and emission spectra of Er3+ ions in SrWO4 crystal have been investigated. The Judd-Ofelt (JO) theory was applied to the polarized absorption spectra of Er3+:SrWO4 to obtain the three JO parameters: Ω2=7.41×10−20cm2, Ω4=0.25×10−20cm2, and Ω6=1.71×10−20cm2. The radiative probabilities, radiative lifetimes, and branch ratios of Er3+:SrWO4 were calculated. The stimulated emission cross sections of the potential laser transitions at 1535nm were determined using the reciprocity method and the Fuchtbauer-Ladenberg formula, and the potential laser gain versus wavelength for the I13∕24→I15∕24 transition has been estimated and discussed.