Total internal reflection in anisotropic crystals

Examples of total internal reflection manifestation have been considered on the basis of a solution to boundary problems of crystal optics using the Berreman matrix method and applying the Mathematica-5 system. It is shown how optical activity manifests itself in the total internal reflection and how this effect can be used to monitor the quality and homogeneity of film coatings.     

Inverse Faraday effect in anisotropic media

The inverse Faraday effect in anisotropic media has been studied theoretically. All the 32 symmetry classes of crystals are considered at various relative orientations of the optic axes and directions of light propagation. The specific features of the inverse Faraday effect in uni-and biaxial crystals are considered.     

The growth kinetics of barium sulphate crystals in suspension: Scale prevention (I)

The growth process of barium of sulfate crystals suspended in a supersaturated solution has been studied conductometrically. The mean linear rate R̄ has been plotted as a function of the growth affinity — Δμ/RT. A first attempt has been made to fit the experimental growth data in the highest supersaturation range with surface nucleation models.     

Modern application packages for rigorous solution of problems of light propagation in anisotropic layered media: II. Optically active crystals

The matrix Δ suggested by Berreman for optically active crystals of various symmetry classes has been calculated with the use of the Mathematica-4.1 package. It is shown that the eigenvalues of this matrix are the refractive indices, whereas its eigenvectors determine the polarization states of eigenwaves propagating in the crystal. The relation between the components of the gyration tensors obtained on the basis of various constitutive equations is established. The essential differences in the optical activity described on the basis of these equations are also discussed.     

Structure and properties of quartz crystals grown from fluoride solutions: I. The morphology of basal pinacoid habit

The mechanism of growth of quartz crystals from fluoride media has been investigated. It is shown by different independent methods (selective etching, X-ray diffraction analysis, optical microscopy) that the faceted forms of autonomous growth regions (trigonal pyramids formed on nonsingular crystal faces) are unstable and degenerate during growth. This degeneracy is accompanied by torsion deformation of autonomous growth regions and, as a result, formation of a series of hollow helical channels at boundaries of autonomous growth regions, whose axes make an angle of ～16° with the OZ axis, and their projections on the XOY plane are directed along the +X axes.     

Bulk photovoltaic effect in noncentrosymmetric crystals

The theory and the experimental characteristics of the bulk photovoltaic effect in ferroelectric and piezoelectric crystals first observed at the Institute of Crystallography have been reviewed. I dedicate this review to the memory of B.K. Vainshtein whose help in performing these works was really inestimable.     

Growth conditions and electric properties of KDP crystals. I. Conductivity measurements

Conductivity of potassium dihydrophosphate (KDP) crystals grown from solutions with different pH has been studied with due regard for the sectorial structure and the impurity composition of the crystals grown. The dependence of the conductivity parameters on these two factors is established. The data obtained lead to a conclusion on the formation of the real structure important for various electro-optical applications of KDP crystals and provide the optimization of growth conditions.     

Configurations of the zero-birefringence and zero-dichroism lines of electromagnetic waves in weakly anisotropic crystals

Configurations of two types of lines—those of zero birefringence and zero dichroism—drawn by the end of the directional vector of the wave normal over the unit sphere, which correspond to the coincident phase velocities or the absorption coefficients of isonormal electromagentic waves in weakly anisotropic crystals, have been studied analytically. It is shown that under the conditions of weak dielectric anisotropy, even slight changes in anisotropy result in the dramatic deformation of the lines of both types. The corresponding evolution of the configurations with the change of the anisotropy parameters is considered by example of absorptive orthorhombic crystals.     

Radiation effects in ZrF4 based glasses: I. Electron spin resonance

Binary ZrF₄BaF₂, HfF₄BaF₂, and multicomponent ZrF₄ based glasses have been studied by electron spin resonance spectroscopy after liquid-nitrogen-temperature X-irradiations and room-temperature γ-ray irradiations. Polycrystalline BaF₂, ZrF₄ and HfF₄ were investigated in the same manner for comparison purposes. Isochronal anneal experiments have distinguished several resonances in the glasses which are characterized as due to F₂^? molecular ions, F⁰ interstitial atoms and Zr³⁺ and Hf³⁺ ions. Two more signals are tentatively assigned as due to a hole trapped on several fluorine ions and a hole trapped on an oxygen impurity. In lead-containing glasses the formation of Zr³⁺ is strongly inhibited, presumably due to the competitive formation of Pb⁺ ions. However, the radiation production of Pb³⁺ ions was independently observed, thus suggesting that the Pb²⁺ ions may serve as traps for charge carriers of either sign. No defects were detected which could be explicitly associated with other cationic constituents, such as La³⁺, Al³⁺, or Li⁺.     

The growth and photorefractive effect of co‐doped Ce:Cu:BSO crystals

In the paper Ce:Cu:BSO crystal has been grown by Czochralski method for the first time with doping CeO₂ and CuO into BSO(Bi₁₂SiO₂₀) crystal. The exponential gain coefficient and respond time of Ce:Cu:BSO crystal are measured by two‐wave‐coupling technology. The results indicate that exponential gain coefficient of Ce:Cu:BSO is more than two times as that of non‐doped BSO and the response time exhibits in microsecond level. Furthermore its exponential gain coefficient improves greatly compared with Ce:BSO's at the same doping level of Ce, while its response time is less than Ce:BSO's. The improvement mechanism of photorefractive effect of Ce:Cu:BSO crystal is investigated systematically. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The effects of microgravity on protein crystallization: evidence for concentration gradients around growing crystals

Atomic force microscopy (AFM) investigations have revealed that macromolecular crystals, during their growth, incorporate an extensive array of impurities. These vary from individual molecules to large particles, and microcrystals in the micron size range. AFM, along with X-ray topology, has further shown that the density of defects and faults in most macromolecular crystals is very high in comparison with conventional crystals. The high defect density is a consequence of the incorporation of impurities, misoriented nutrient molecules, and aggregates of molecules. High defect and impurity density, contributes to a deterioration of both the mechanical and the diffraction properties of crystals. In microgravity, access by impurities and aggregates to growing crystal surfaces is restricted due to altered fluid transport properties. We designed, and have now constructed an instrument, the observable protein crystal growth apparatus (OPCGA) that employs a fused optics, phase shift, Mach–Zehnder interferometer to analyze the fluid environment around growing crystals. Using this device, which will ultimately be employed on the international space station, we have, in thin cells on earth, succeeded in directly visualizing concentration gradients around growing protein crystals. This provides the first direct evidence that quasi-stable depletion zones formed around growing crystals in space may explain the improved quality of macromolecular crystals grown in microgravity. Further application of the interferometric technique will allow us to quantitatively describe the shapes, extent, and magnitudes of the concentration gradients and to evaluate their degree of stability.     

Memory-switching effect in single crystals of thallium selenide

It has been found that thallium selenide single crystals exhibit bistable or memory switching. The specimen under test showed threshold switching with critical field of the switching being ∼ 10³ V/cm at room temperature. Memory switching effect measurements were performed with single crystals of p–TlSe. The results strongly indicated that the phenomenon in our sample is very sensitive to temperature, light intensity and sample thickness. Memory state persists if the current is decreased slowly to its zero value. However, if current was forced to decay suddenly, the specimen returned to the high resistance state. The current-voltage characteristics is symmetrical with respect to the reverse of the applied voltage and current. The switching parameters were checked under the influence of different factors of the ambient condition. An analysis of the results was done.     

The effect of composition on spinel crystals equilibrium in low-silica high-level waste glasses

The liquidus temperature (T_L) and the equilibrium mass fraction of spinel were measured in the regions of low-silica (less than 42 mass% SiO₂) high-level waste borosilicate glasses within the spinel primary phase field as functions of glass composition. The components that varied, one at a time, were Al₂O₃, B₂O₃, Cr₂O₃, Fe₂O₃, Li₂O, MnO, Na₂O, NiO, SiO₂, and ZrO₂. In the low-silica region, Cr₂O₃ increased the T_L substantially less, and Li₂O and Na₂O decreased the T_L significantly less than in the region with 42-56 mass% SiO₂. The temperature at which the equilibrium mass fraction of spinel was 1 mass% was 25-64 °C below the T_L.     

Formation of temperature fields in doped anisotropic crystals under spatially inhomogeneous light beams passing through them

The features of formation of thermal fields in potassium dihydrophosphate crystal doped with potassium permanganate under a 532-nm laser beam passing through it have been investigated. Data on the influence of birefringence on the temperature distribution in an anisotropic crystal whose surface is illuminated by a spatially modulated light beam are presented.     

Temperature distribution in growing semi-transparent crystals (I). Theory

Simplified analytical and computational solutions of the temperature distribution in crystals grown by Czochralski method including the temperature difference on the liquid/solid interface are given. The model used is based on experiments with oxide crystals with melting points above 2000 K. Computational solution was more extended because it enables to calculate actual temperature distribution with a relatively small error.     

In doping effect on optical properties in Zn:In:Fe:LiNbO3 crystals

A series of Zn:In:Fe:LiNbO₃ crystals were prepared by Czochralski method. The crystal composition and defect structure were analyzed by ICP‐OE/MS, UV–vis and IR spectroscopy. The results show that with increasing In³⁺ doping concentration in melt, the segregation coefficients of both Zn and In ions decrease. The optical damage resistance of Zn:In:Fe:LiNbO₃ crystals was studied by the transmitted beam pattern distortion method. It is found that the optical damage resistance of Zn:In(3mol%):Fe LiNbO₃ crystals is two orders of magnitude higher than that of Zn:Fe:LiNbO₃. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)