X.B. Hu

Characterization of Growth Defects in Nd:YCa4O(BO3)3 Crystals by Transmission Synchrotron Topography

The growth defects in Nd: YCa 4 O(BO 3 ) 3 (Nd: YCOB) crystals were investigated by transmission synchrotron topography. It was found that growth striations were the primary defects in Nd:YCOB crystals. Grown-in dislocations, mosaic blocks and inclusions were also observed in the crystals. The effect of temperature field on the formation of growth defects in the crystals was discussed.

Self-frequency doubled green NdxY1-xCa4O(BO3)3 laser

Nd-doped yttrium calcium oxyborate, Nd x Y 1-x Ca 4 O(BO 3 ) 3 (NYCOB), was grown using pulling from the melt, with large sizes and good optical quality as well as different Nd 3+ -ion densities of 0 to 10 at% in the lattice structure. These crystals belong to the monoclinic system with point group m, conforming space group C m . The unit cell constants were a = 0.8076(7), b = 1.6020(10), and c = 0.3527(2) nm for a Nd 3+ content of 8 at%, with β = 101.23°, and z = 2. The measured absorption of the NYCOB was compared to Judd-Ofelt (JO) theory. When applied, the JO theory of parity-forbidden electric-dipole transitions of rare earth ions on non-centrosymmetric sites demonstrates good agreement. The polarized absorption coefficients at 811 nm were calculated as α X = 1.59, ay = 1.75, and α Z = 2.02 1/cm, respectively. The valence-conduction band gap is about 5.39 eV. The fitted intensity parameters Ω t (t = 2, 4, and 6) were 3.51×10 -20 , 7.82×10 -20 , and 3.79×10 -20 cm 2 , with a root-mean square deviation of 6.30 x 10 -21 cm 2 . The emission properties of the excited 4 F 3/2 state with the level lifetime of 216.67 μs were studied, which exhibit the two pass bands of laser for possible applications in practice. The self-frequency doubling tests are interesting. A very low threshold power of 2 mW for a sample with average Nd 3+ content of 7 at%, length of 6 mm, and phase matching angles of 0 = 64.5° and φ = 35.5° have been measured. The measured output power of green light was 19.4 mW accompanied with a conversion efficiency of 3.7%.

Growth defects in flux grown RbTiOAsO4 crystals observed with white-beam synchrotron radiation topography

Abstract The growth defects in flux grown RbTiOAsO 4 crystal have been investigated by white-beam synchrotron radiation topography. It is found that growth sector boundaries are the primary growth defects and they show strong X-ray kinematical contrast in the topograph. All the dislocations are growth induced and appear only in the near capping region. The area away from the capping region is nearly dislocation free. Growth bands show weak contrast in the X-ray topograph, which implies that the impurity contents are relatively low in various growth sectors and each growth sector is uniform in composition.

Comparative Study of KTiOPO4 crystals

High purity KTiOPO 4 (KTP) crystals have been grown using a flux method. The quality, SHG efficiency and damage threshold of KTP crystals grown from high purity reagents were compared with those grown from commercial reagents. Experimental results indicate that KTP crystals using a high purity charge contain less impurities and possess higher SHG efficiency and damage threshold than do crystals grown from commercial reagents. It is proposed that decreasing the concentrations of impurities is an effective way of raising the damage threshold for KTP crystals.

Spectroscopic Properties and Diode Laser-Pumped Operation of Nd : YAl3(BO3)4 Crystal

Nd-doped yttrium aluminum borate, Nd x Y 1-x Al 3 (BO 3 ) 4 (NYAB), with large sizes and good optical quality has been grown by the flux method. When the Judd-Ofelt (JO) theory of parity-forbidden electric-dipole transitions of rare earth ions on non-centrosymmetric sites was applied to NYAB, it resulted in a good fit on absorption of the crystal. According to the JO theory, the fitted intensity parameters Ω t (t = 2, 4, and 6) were calculated as 2.19 x 10 -20 , 1.97 x 10 -20 , and 3.10 × 10 -20 cm 2 , respectively, with a root mean square deviation of 1.22 x 10 -21 cm 2 . The emission properties of the excited 4 F 3/2 state have been studied, and the spectral parameters of NYAB crystal were compared with those of Nd x Gd 1-x Al 3 (BO 3 ) 4 (NGAB) crystal. A cw NYAB laser at 1.06 μm end-pumped by a high-power diode laser array has been demonstrated. A maximum output of 3.2 W at 1.06 μm has been achieved with an optical conversion efficiency of 29.1% and an average slope efficiency of 37.5%. It is found that these results approach those of Nd:YVO 4 crystal.

Investigation on the Spontaneous Strain and Ferroelastic Domain Structures in NdP 5 O 14 Crystals by High Resolution X-Ray Diffractometry

Large NdP 5 O 14 crystal with dimension of 15 2 25 2 60 mm 3 has been grown by flux method. The spontaneous strains and ferroelastic domain structures have been investigated by high resolution X-ray diffractometry for the first time. The reflection peak separations resulting from the misorientation between matrix domain and ferroelastic domain were observed in the rocking curves for several different reflections. Based on the features of the reflection peak separations, the ferroelastic domain structures were determined. It is found that most of the ferroelastic domains in NdP 5 O 14 are of type-a, while type-b ferroelastic domains only appear in the serious strain regions. Based on the domain structures of NdP 5 O 14 , the reflection peak separations for 802, 402 and 204 reflections were calculated respectively. And the experimental observations are in agreement with the calculations very well. In addition, the spontaneous strain in NdP 5 O 14 was determined to be 0.0082 by measuring the peak separation ...

Optical Parameters of Nd‐Doped Gadolinium Aluminium Tetraborate Crystals

Nd-doped gadolinium aluminium tetraborate, Nd x Gd 1-x Al 3 (BO 3 ) 4 (NGAB), crystallizes with x = 0.1 in the trigonal system with point group 32, conforming space group R32. They were grown using flux method, of large sizes and good optical quality. The unit cell constants were a = 0.93057 (6) and c = 0.72481 (3) nm, and z = 1. The measured absorption of the NGAB is compared to Judd-Ofelt (JO) theory. When applied, the JO theory of parity-forbidden electric-dipole transitions of rare earth ions on noncentrosymmetric sites demonstrates good agreement. A measured band gap of the eigentransition was about 4.00 eV. The fitted intensity parameters Ω t (t = 2.4, and 6) were 2.446 × 10 -20 , 2.266 × 10 -20 and 2.598 × 10 -20 cm 2 . Both the emission properties of the sub-stable 4 F 3/2 state with the level lifetime of 506.20 μs and a fluorescence spectrum corresponding to the transition 4 F 32 → 4 I 11/2 were studied. The results indicate the pass band of laser for potential applications in practice.