Bing Teng

Optical and laser properties of Nd:GdVO4 crystal

Abstract Nd-doped gadolinium vanadate Nd:GdVO 4 crystal with large sizes and good optical quality has been grown by Czochralski method. When the Judd–Ofelt theory of parity-forbidden electric-dipole transitions of rare earth ions on non-centrosymmetric sites is applied to the Nd:GdVO 4 , it results in a good fit on the absorption of the crystal. The spectral parameters of Nd:GdVO 4 crystal have indicated that it is an excellent candidate laser material. The three intensity parameters Ω t are fitted as 12.629×10 −20 , 4.828×10 −20 and 8.425×10 −20 cm 2 at t =2, 4 and 6, respectively. In laser experiment, the highest output power of up to 14.3 W at 1.06 μm has been achieved with a 4 mm thick Nd:GdVO 4 crystal sample when it is pumped by a 26 W cw fiber-coupled laser-diode array. The light–light conversion efficiency is 55%, and the average slope efficiency is 62%.

Spectroscopic properties of Yb-doped GdCa4O(BO3)3 crystal

Abstract The doped nonlinear optical (NLO) crystal Yb:GdCa 4 O(BO 3 ) 3 (Yb:GdCOB) has been grown by using the Czochralski method, with large sizes and good optical quality. The polarized absorption and fluorescence spectra have been measured and analyzed according to the Judd–Ofelt theory. The ground-state energy-level splitting is 1002 cm −1 . The spectral parameters of the crystal such as the emission lifetime, the absorption cross-section, and the peak emission cross-section have been calculated. In comparison with established laser crystals the results suggest that this crystal has potential as an efficient self-frequency-doubling (SFD) laser operation in the green.

Actively Q-switched intracavity second-harmonic generation of 1.06 μm in BiB3O6 crystal

Abstract We have investigated the acousto-optically Q-switched intracavity second-harmonic generation of 1.06 μm in a 1.9-mm-long BiB3O6 crystal, cut for type-I phase-matching direction of (θ,ϕ)=(168.9°,90°), performed in a diode-end-pumped Nd:YVO4 laser. When the incident pump power was 4.3 W at 30 kHz of pulse repetition frequency, a maximum average green output power of 480 mW , the shortest pulse with FWHM width of 72 ns , the highest single pulse energy of 16 μJ and the maximum peak power of 222 W were obtained, giving the corresponding optical conversion efficiency of 11.2%. The effect of varying temperature in BIBO crystal on the average green output power was also investigated.

Bismuth octaborate, Bi2B8O15.

In the title compound, Bi(2)B(8)O(15), the Bi atom is coordinated to five or six O atoms. The B atoms exhibit two kinds of hybridization, sp(2) and sp(3), seen in the BO(3) triangles and BO(4) tetrahedra, respectively. Three BO(3) triangles are connected to form a B(3)O(6) planar ring. All atoms in the structure are connected together to form an infinite three-dimensional network.

Anisotropic thermal expansion of BiB3O6

The anisotropic thermal expansion of BiB3O6 (BIBO) has been studied in the temperature range 25 °C to 299.5 °C. The three values of principal expansion coefficients α1, α2, and α3 and the orientation of the principal axes are −26.43×10−6 K−1, 50.4×10−6 K−1, 8.53×10−6 K−1, and 8.9°, respectively. Large anisotropic thermal expansion will cause thermal stress, leading to crystal fracture and the formation of parasitic crystallites along the direction of crystal grain growth. The results obtained from transmission electron microscopy support the evidence observed from the measurements of expansion. This may be useful for BIBO crystal growth.

Raman study of phonons in bismuth triborate BiB3O6 crystal

A Raman-scattering study of the vibrational modes in a BiB3O6 crystal was conducted at room temperature. The numbers of external and internal modes obtained in experiment are consistent with the results of a group theoretical analysis. The Raman lines below ∼300cm−1 and from ∼300to1600cm−1 are assigned to the external modes of the lattice and internal vibrations of the BO3 and BO4 subunits of the BiB3O6 structure, respectively.

Diode-laser-array end-pumped 1W CW Nd:YVO4/BIBO green laser

Abstract This paper discusses a diode-laser-array end-pumped Nd:YVO4/BIBO green laser. Using a three-mirror folded cavity (V-shaped), a 1.06 W CW green output was obtained at an incident pump power of 8.5 W; the corresponding optical conversion efficiency was 12.5%. The relationship between the green output and the temperature of the BIBO crystal was investigated. The laser damage threshold of BIBO crystal was measured to be 600 MW cm−2 and 400 MW cm−2 at 1064 nm and 532 nm, respectively.

Observation of inhomogeneity in congruent LiTaO3 crystal

Abstract The inhomogeneity in a congruent LiTaO 3 crystal has been observed by transmission synchrotron topography. Many extraordinary regions exist in congruent LiTaO 3 crystal and they often show diffraction intensity different from that of ordinary regions in synchrotron topographs. Differential thermal analysis indicates that the Curie temperature of the extraordinary region is lower than that of ordinary region, and the extraordinary region is really a high defect density region. The diffraction contrast of the extraordinary region in synchrotron topographs is explained qualitatively by a calculation at the selected wavelength.

Growth defects in BiB3O6 crystals observed with white-beam synchrotron topography

Abstract The growth defects in BiB 3 O 6 (BIBO) crystals have been investigated by white-beam synchrotron radiation topography for the first time. It is found that inclusions, dislocations and growth sector boundaries are the primary growth defects nearby the seed. The area away from the seed is nearly free of defects. Based on the experimental observations, the formation mechanism of brown region in BIBO crystals is discussed. Twins and growth sector boundarie exist in the brown region, which is the key reason resulting in brown presentation. The approaches to reduce and eliminate the defects are presented.

Growth and defects in YbxY1−xAl3(BO3)4 crystals

YbxY1-xAl3(BO3)(4) (x = 0.1, 0.07 and 0) crystals have been grown by the flux method. The growth defects of YbxY1-xAl3(BO3)(4) crystals were detected by X-ray topography. It is found that the perfection of YbYAB crystal with low Yb dopant is better than that with high Yb dopant. In Yb0.1Y0.9Al3(BO3)(4) crystal, growth bands, growth boundaries, grown-in dislocations and inclusions were observed. However, the densities of growth defects for Yb0.07Y0.93Al3(BO3)(4) and YAl3(BO3)(4) are low and no obvious inclusions are observed in these crystals. In addition, growth twins were detected in YbxY1-xAl3(BO3)(4) crystal by using the chemical etching method. It is found that the growth twins occur frequently in Yb0.1Y0.9Al3(BO3)(4) crystal whereas no growth twin appears in YAl3(BO3)(4) crystal. Based on the experimental observations, the formation mechanism of growth twins is discussed. In the meantime, the effective measures for reducing the growth twins and defects are proposed