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Nanocrystalline zirconium-silicon-boron thin films were studied to determine their elastic properties.

Single soliton solutions to the nonlinear Schrodinger equation with additional higher order nonlinear and dispersion terms were employed to model the characteristics of microwave magnetic envelope solitons in thin films, particularly for the power-dependent soliton velocity in this films. The model was based on an empirical scaling between the dimensionless amplitude parameters in the higher order nonlinear Schrodinger equation and the pulse power levels in the experiment.

Defects created by through-implantation in both the oxide and the substrate are analyzed using positron method. The profile of the defects is inferred from the oxide and from the Si substrate. In the oxide layer, defects produced by the electronic and the nuclear stopping of the implanted ions are observed. Improved depth resolution is obtained through controlled etching process and a limit to the thickness of oxide is inferred. The results are discussed.

The mechanism of sulphur diffusion at the interface between a silicon heterolayer and a sulphur-protected gallium arsenide(100) layer was investigated. Specifically, particle induced x-ray emission and Rutherford backscattering spectrometry were employed to observe the depth distribution of sulphur. In addition, x-ray absorption near-edge structure and x-ray photoemission spectroscopy were used to examine the interfacial structure.

The influence of arrangement of micro-pillars on wetting and self-motion of droplets is numerically studied via a three-dimensional lattice Boltzmann model for multiphase flow. Substrates textured with identical pillar array density but different arrangements are considered. The results show that the prediction of Cassie-Baxter model can be improved with the modified roughness factors. In addition, transportation of droplets on the stepwise gradient structured substrates is investigated. A simple model, taking account of pillar arrangement, is developed to estimate droplet velocity. The results show that it is critical to restrain droplet spreading in the lateral direction to achieve higher velocity and longer transportation distance. [ABSTRACT FROM AUTHOR]

We report the growth of a Nd-doped calcium barium niobate (Nd:CBN-28) single crystal using the Czochralski method. The point group and space group of Nd:CBN-28 are determined to be tetragonal 4mm and P4bm, respectively, and the effective segregation coefficients of Nd, Ca, Ba, and Nb are 0.988, 1.029, 0.992, and 0.985, respectively. The density of the material is 5.321 g cm-3 at 19.6 °C, in good agreement with the theoretical value. Thermal expansion measurements reveal that during the heating cycle, the c-axis of Nd:CBN-28 undergoes both thermal contraction and thermal expansion, while at the same time there is only expansion along the a-axis. Specific heat measurements reveal that an anomaly appears at about 220 °C due to a phase transition. The thermal diffusivity increases slowly with increasing temperature. The thermal conductivity of the crystal has been calculated from these results, and the phonon mean free paths la and lc along the a- and c-axes of Nd:CBN-28 crystal are estimated. The transmission spectrum of Nd:CBN-28 crystal along the [001] direction has been measured. [ABSTRACT FROM AUTHOR]

A series of laser crystals Nd:LuxGd1-xVO4 (x=0.14,0.32,0.50,0.61,0.70,0.80) was grown by the Czochralski method. The thermal properties, including the average linear thermal expansion coefficients, thermal diffusion coefficients, specific heats, and thermal conductivities, of the mixed crystals were obtained. The material constants Ms for the thermal stress resistance figure were calculated and showed that the thermal fracture limits of the mixed crystals should be comparable with that of Nd:YVO4. The polarization absorption spectra from 240 to 1000 nm were measured at room temperature and the absorption cross sections at 809 nm were calculated. Using the Judd-Ofelt theory, the theoretical radiative lifetimes were calculated and compared with the experimental results. Continuous wave laser performances were achieved with the mixed crystals at the wavelength of 1.06 μm when they were pumped by a laser diode. Thermal, optical, and laser properties have shown variation as a function of x and proved that the mixed crystals are good laser materials. [ABSTRACT FROM AUTHOR]

A strontium tungstate (SrWO4) single crystal with dimensions of [uppercase_phi_synonym] 25×40 mm2 has been grown by the Czochralski method using an iridium crucible. X-ray powder diffraction results show that as grown the SrWO4 crystal belongs to the tetragonal system in the scheelite structure. The effective segregation coefficients of elemental W and Sr in the crystal growth are measured by x-ray fluorescence, and the respective values are close to 1. The thermal properties of the SrWO4 crystal were systemically studied by measuring the thermal expansion, specific heat, and thermal diffusion coefficient. These results show that the crystal possesses a large anisotropic thermal expansion with thermal-expansion coefficients αa=8.61×10-6/K, αb=8.74×10-6/K, αc=18.78×10-6/K over the temperature range of 303.15–773.15 K. The measured value of the specific heat is 0.30–0.34 J g-1 K-1 when the temperature is increased from 323.15 to 1073.15 K. The thermal diffusion coefficient was measured over the temperature range of 303.15–543.15 K. The thermal conductivities of the SrWO4 crystal along the [100] and [001] directions are calculated to be 3.1326 W m-1 K-1 and 2.9477 W m-1 K-1, respectively, at 303.15 K. Then the thermal properties of some other Raman crystals were compared with these data, and the thermal focal lengths for these crystals were also estimated. [ABSTRACT FROM AUTHOR]

Yb doped KLu(WO4)2 (Yb:KLuW) single crystal was grown by the method of top-seeded-solution growth slow-cooling method. Its lattice vibrational modes were calculated by using space group theory, and polarized Raman spectra were measured at room temperature with different scattering geometry projections. The powder transmission of Fourier-transform infrared spectra was also performed as a supplement for Raman spectra to study the lattice vibration of the laser crystal. The main Raman peaks and infrared transmission bands were attributed to the internal mode WO6 octahedrons in the crystals. Two kinds of link ways of WO6 octahedrons implying large distortion had led the Raman peaks to shift to different positions. Large distortions of the WO6 octahedrons in the crystal had led to the splitting of some Raman peaks and even the activation of ν6 mode, which is originally a silent mode by the selection rule. As a self-Raman crystal, the linewidth of the Raman peaks ν1 and ν2 reached 12.5 and 16.6 cm-1, with relaxation times of 849.4 and 639.6 fs, respectively, indicating that it is a promising stimulated Raman scattering crystal. Thermal diffusion measurement of Yb:KLuW showed large anisotropy which could be explained by the different link ways of the WO6 octahedrons. [ABSTRACT FROM AUTHOR]

At room temperature, Raman-scattering investigations of near stoichiometric lithium niobate (S-LN) crystals theoretically and experimentally reveal an effect of the lattice vacant positions on the Raman spectra. At high temperature, Raman peaks of the mode ν5 vary sensitively and intensely with the increase of the temperature. A condensed soft optical-phonon mode originates from the triply degenerate symmetric in-plane O–Nb–O bending. The paraelectric-ferroelectric structural transition occurs at about 1170 °C. The composition homogeneity and optical uniformity of the S-LN crystals are demonstrated to be excellent compared with those of the congruent lithium niobate. [ABSTRACT FROM AUTHOR]

A large single crystal of barium tungstate (BaWO4) with dimensions of 22-mm diameter×80-mm length was grown by the Czochralski method using an iridium crucible. The melting point, molar enthalpy of fusion, and molar entropy of fusion of the crystal were determined to be 1775.10 K, 96 913.80 J mol-1, and 54.60 J K-1 mol-1, respectively. The average linear thermal-expansion coefficients are αa=10.9526×10-6/K, αb=10.8069×10-6/K, and αc=35.1063×10-6/K in the temperature range from 303.15 to 1423.15 K along the three respective crystallographic axes. The density of the crystal follows an almost linear decrease from 6.393×103 to 6.000×103 kg m-3 when the temperature is increased from 303.15 to 1423.15 K. The measured specific heat are 115.56–130.96 J K-1 mol-1 in the temperature range of 323.15–1173.15 K. The thermal diffusion coefficient of the crystal was measured in the temperature range of 297.15–563.15 K. The calculated thermal conductivity is 2.256 W m-1 K-1 along the [001] direction and 2.324 W m-1 K-1 along the [100] direction at 323.15 K. The microhardness of the BaWO4 single crystal in the (001) and (100) planes is 1393 and 1814 MPa under a load of 0.050 kg. [ABSTRACT FROM AUTHOR]

X-ray diffraction measurements on a 0.65 at. % Nd-doped GdCa[SUB4]O(BO[SUB3])[SUB3] (Nd:GdCOB) crystal revealed a noncentrosymmetric monoclinic space group Cm with lattice parameters a=8.091 ±0.001, b = 16.023±0.002, c = 3.559±0.006 Å, and β = 101.30±0.01°. The fitting primitive cell contained two Nd:GdCOB units. Raman data show that the characteristic spectra of Nd:GdCOB are mainly associated with BO[SUB3] triangles and partly by Ca(1)O[SUB6] octahedra, which implies that the structural rigidity of Nd:GdCOB is mainly associated with the B-O bond stretching and bending modes and partly by the Ca(1)-O bonds. The large distortions of the Gd/NdO[SUB6] and Ca(2)O[SUB6] octahedra intensify the polar forces and anisotropic lattice forces, which indicates excellent nonlinear properties for Nd:GdCOB. Simultaneously, the large distortions of the Gd/NdO[SUB6] octahedra also provide a suitable crystal field for the activated Nd[SUP3+] ions, with the site symmetry m lacking inversion symmetry. This condition increases the probability of the parity-forbidden f →f transitions. Also due to the greater number of anion groups in the primitive cell, this crystal would be expected to be excellent as a self-frequency doubled material. The absorption parameters calculated by Judd-Ofelt theory show that the transitions [SUP4]I[SUB9/2]→[SUP4]F[SUB5/2] and [SUP4]I[SUB9/2]→[SUP2]H[SUB9/2] have larger absorption cross sections and enable the laser-diode pumping band around 808 nm to be more than 30 nm in bandwidth. In the calculated luminescence parameters, the radiation [SUP4]F[SUB3/2]→[SUP4]I[SUB11/2] transition at wavelength of 1060 nm has the largest fluorescence branch-ratio and differential stimulated-emission cross section. [ABSTRACT FROM AUTHOR]

Based on the quantum electrodynamics and using Einstein’s coefficient and Planck’s energy density, the stimulated emission cross section was given. The measured absorption of 0.5 at. % Nd-doped Nd:GdVO[sub 4] crystal was compared to the Judd–Ofelt (JO) theory. When applied, the JO theory of parity-forbidden electric–dipole transitions of rare-earth ions on noncentrosymmetric site lacking inversion symmetry demonstrates good agreement. An absorption band around 808 nm is suitable to match laser diode pumping. The branching ratio of the fluorescence emission and stimulated emission cross section at the emissive wavelength of 1064 nm are of great advantage to produce a laser output. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Examines spectral parameters of neodymium-doped yttrium orthovanadate (NYV) crystals. Absorption spectrum of neodymium ions doped in NYV; Width of the absorption band; Line intensity of the absorption spectrum of NYV.

Presents information on a study on the Raman-scattering investigations and the optical and laser properties of Yb-doped YVO...crystal. Experimental method; Results; Discussion; Conclusions.

Scattering from longitudinal guided modes (LGM) are observed in Brilloun scattering on ZnSe-ZnSe(1-x)S(x) strained-layer superlattices. The velocities of the LGM are obtained by the C11 elastic constant. The C11 and C44 elastic constants are calculated using the velocity of the first-order LGM of the quasilongitudinal acoustic mode and the quasitransverse acoustic mode of ZnSe-ZnSe(1-x)S(x) superlattice films.