Jingqian Wei

Growth and characterization of cubic KTa1-xNbxO3 crystals

Abstract The top-seeded flux method was used to grow large size and good quality undoped, Cu or Fe doped cubic phase KTa 1- x Nb x O 3 crystals. The morphology, homogeneity, dielectric properties and electrooptic properties of these crystals have been investigated. The photorefractive properties of a Cu-doped KTN crystal have also been studied and the results obtained show that the diffraction efficiency of this crystal is above 50% at room temperature.

Growth, defects, and properties of GdCa4O(BO3)3 and Nd:GdCa4O(BO3)3 crystals

Pure and neodymium-doped gadolinium calcium oxoborate crystals of high quality were grown by the Czochralski method. The orientation of crystal was precisely determined, and the samples for measurements were prepared. Through synchrotron x-ray topography and high-resolution x-ray diffractometry, the twin structure was discovered. Some properties such as the figure of merit value, and dielectric, piezoelectric, and elastic constants were measured along with a discussion of the anisotropy of the laser properties.

PHOTOREFRACTIVE PROPERTIES AND SELF-PUMPED PHASE CONJUGATION OF TETRAGONAL FE-DOPED KTA1-XNBXO3 CRYSTAL

This letter reports the two‐wave mixing experimental results of tetragonal Fe‐doped KTa1−xNbxO3. A 7.3 cm−1 gain coefficient and 42% diffraction efficiency have been obtained. For the first time internally self‐pumped phase conjugation is being observed in this crystal. At room temperature, the conjugate reflectivity measured is 21%.

Research on growth and self-frequency doubling OF Nd:ReCOB (Re=Y OR Gd) crystals

Large (up to 45mm in diameter and 50mm in length) ReCa4O(BO3)3 (ReCOB) and Nd:ReCOB (Re=Y or Gd) crystals with high optical quality were grown by well designed procedures. Crystal orientation was carefully determined. Based on the measurements of refractive indices the phase matching (PM) figures for both crystals were calculated. Theoretical calculation of the spatial distribution of the effective nonlinear coefficients, which show an asymmetric feature, was carried out to determine the optimal PM orientations which were experimentally confirmed, i.e. (66.3°, 134.4°) and (64.5°, 33.5°) for GdCOB and YCOB respectively.

The electric properties of rubidium titanyl phosphate crystals

Abstract Rubidium titanyl phosphate (RbTiOPO4, RTP) large single crystals have been grown by flux method. The influence of temperature and frequency on the electric properties of RTP single crystal have been studied by measuring dielectric constants, dielectric losses, impedances, conductivities and pyroelectric coefficients. Our experimental results have shown that the ferroelectric phase transition of RTP crystal is of the displacive-type and of second order, and its temperature is 829 ± 1°C. Above 200°C, the super-ionic conducting direction is along the ferroelectric axis direction, and the dielectric relaxation is of non-Debye type. Below 150°C, RTP crystal has a normal pyroelectric effect, while above this temperature a strong thermo-stimulated current will occur for a single domain sample.

The second-harmonic-generation property of GdCa4O(BO3)3 crystal with various phase-matching directions

Abstract The method to determine the spatial configuration of GdCa4O(BO3)3 (GdCOB) crystal is introduced. Samples are cut in and out of principal planes for type I phase matching. Their second-harmonic-generation (SHG) conversion efficiency is measured by a mode-locked Nd:YAG laser. The intracavity doubling frequency of GdCOB crystal is reported for the first time. At the incident pump power of 10 W, the 532 nm output reaches 1.22 W with the (113.2°, 47.4°)-cut sample. In conclusion, the (113.2°, 47.4°)-cut sample shows more excellent SHG property than those cut in other directions.

Optical properties of NdxGd1−xAl3(BO3)4 crystal

The optical properties of NdxGd1-xAl3(BO3)4(NGAB) crystal are reported. The refractive index of it were mesured by V-prism method. The absorption spectra and the flourescence specra of NGAB were also obtained. The optical parameters of NGAB were calculated following J-O theory, the three optical parameters are Ω2 = 1.805 × 10−20, Ω4 = 1.85 × 10−20, Ω6 = 3.793 × 10−20(RMS= 1.4 × 10−7) and βc(4F3/2 →4I11/2) is about 0.53.

Absorption and emission properties of erbium calcium oxyborate crystals

Abstract Erbium calcium oxyborate ErCa 4 O(BO 3 ) 3 (ECOB) crystallized with a fluorapatite-type structure in the monoclinic system. The unit cell constants were a =0.8095(3), b =1.6023(5), and c =0.3562(2) nm with the angle β of 101.23°. The primitive cell contained two ECOB formula units. The measured absorption spectra of ECOB were 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 experiments showed that the radiation 2 H 9/2 → 4 I 13/2 transition with green ray of 554 nm and 2 H 9/2 → 4 I 15/2 transition with ultraviolet ray of 410 nm are likely to provide some practical application as a laser material, and that the substable 4 S 3/2 state having the large radiative lifetime of 3.55 ms and the radiation 4 S 3/2 → 4 I 15/2 transition with the large fluorescence branch ratio of 75.67% and green ray of 544 nm are also worth to study for us.

Soft-Mode Spectroscopy in Fe:KTa1-xNbxO3 Crystals

Fe-doped potassium tantalite niobate, Fe:KTa 1-x Nb x O 3 (Fe:KTN), crystallizes with x = 0.48 and a perovskite-type structure in tetragonal system with point group 4mm, conforming space group P4mm. The paraelectric-ferroelectric structural transition of the Fe:KTN is studied by Raman scattering investigations. A condensed soft lattice vibrational mode at the phase transition has been analyzed. It originates from the symmetric O2/O3-Nb/Ta-O3/O2 in-plane bending of the Nb/TaO 6 group. The soft optical phonon mode concerns the extraordinary transverse optical phonons propagating along the [110] direction. The Raman spectra measured reflect the crystal disorder. Curie temperature measured by two methods is within 353 and 3 56.5 K.

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.