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Oxoborate crystal SmCa 4 O(BO 3 ) 3 (SmCOB) has been grown by the Czochralski (CZ) method for the first time. The X-ray powder diffraction (XRPD) of sintered material and single crystal were performed at room temperature. The DSC experiment showed that SmCOB melts congruently at 1397°C. The data of thermal expansion coefficients along X , Y and Z direction have been measured to be 1.03×10 −5 , 3.8×10 −6 and 8.2×10 −6 K −1 , respectively. The specific heat of the crystal as been measured to be 66 cal/mol K at 300 K. The linear optical properties of SmCOB crystal are reported. The measured transmittance spectra from 400 to 2600 nm showed that the crystal has strong absorption peaks which are anisotropic along different crystallophysic axes in the range of 900–1700 nm.

New nonlinear optical crystals GdCa4O(BO3)3 grown by the Czochralski method in a platinum crucible under air atmosphere are reported in this paper. The growth mechanism is a typical two-dimensional nucleation layer growth. The twin and inclusion defects of this crystal are observed using optical microscopy. The incidence of twinning is in good agreement with Hurle's model. The approaches to reduce and eliminate the defects are presented.

The rare-earth ions (Yb3+, Tm3+) and Li+, Bi3+ ions doped GdCa4O(BO3)3 crystals were grown using the Czochralski pulling method. The second-harmonic generation conversion efficiencies of the GdCOB:Yb and GdCOB:Tm crystals are 31.3% and 33.3%, respectively, while the undoped GdCOB crystal is 27.9%. The conversion efficiencies of Yb3+, Tm3+ doped GdCOB are improved by 12% and 19%, respectively, compared to that of the undoped one. The conversion efficiencies of Li+, Bi3+ doped GdCOB crystals are 33% and 38.3%, which are improved by 15% and 37% as compared to that of the undoped crystal. The results are discussed using the anion group theory.

Large sized and optical quality GdCa4O(BO3)3 (GdCOB) crystal with calcium partially substituted by strontium (Sr) ions was grown for the first time. The x-ray powder diffraction shows that the Sr ion has an effect on the cell parameters of the GdCOB crystal. Second-harmonic generation (SHG) experiments were performed on the Sr:GdCOB and GdCOB crystals along the spatial phase-matching direction. The results show that the cw green laser output power is 1.04 W when the laser diode pump power is 10 W in the Nd:YVO4/Sr:GdCOB intracavity laser. Considering the slope efficiency of Nd:YVO4 and the fundamental laser in cavity, the intracavity SHG conversion efficiency of the GdCOB crystal is 21% while it is 24% for the Sr:GdCOB crystal, the SHG conversion efficiency is improved by 14%. The effect of the Sr ions on the nonlinearity of the GdCOB crystal is also discussed by using the anion group theory. PACS: 42. 65. Ky, 78. 20. -e, 78. 55. Hx

Absorption spectra, emission spectra, excitation spectra, and upconversion luminescence of Er 3+ , Tm 3+ co-doped NaY(WO 4 ) 2 crystal were measured at room temperature. Intensity parameters are calculated from absorption spectra in terms of Judd-Offelt theory. Transition processes of the energy levels of Er 3+ and Tm 3+ were analyzed in details and the cross relaxations: 1 G 4 (Tm 3+ )＋ 4 I 15/2 (Er 3+ )→ 3 F 4 (Tm 3+ ) + 4 F 9/2 (Er 3+ ) , 1 G 4 (Tm 3+ )＋ 4 I 15/2 (Er 3+ )→ 3 H 5 (Tm 3+ )＋ 4 I 9/2 (Er 3+ ), 3 F 4 (Tm 3+ )＋ 4 I 9/2 (Er 3+ )→ 3 H 6 (Tm 3+ )＋ 4 S 3/2 or 2 H 11/2 (Er 3+ ) and 4 F 9/2 (Er 3+ )＋ 3 H 6 (Tm 3+ )→ 4 I 15/2 (Er 3+ )+ 3 F 3 (Tm 3+ ) were put forward. Sufficient proofs have been found to illustrate the use of Er 3+ as a sensitizer which is effective for the Tm 3+ -doped crystal.