Congruent Lithium Niobate Crystals Research Articles

A synchrotron X-ray diffraction study of a small congruent LiNbO3crystal: A compatible approach to powder diffraction

Single-crystal synchrotron X-ray diffraction (XRD) data were collected and refined for congruent lithium niobate crystals 8 and 6 μm in diameter, sizes that are comparable to the size of the powder particles used in powder diffraction. The motivation for using such small crystals is to minimize problems such as extinction, which decrease with crystal size. The R/wR factors were 0.011/0.014 and 0.019/0.018, for the 8 and 6 μm data, respectively, and the goodness of fit factors were 2.3(1) and 1.63(8), which compare favorably with values obtained from previous powder and single-crystal diffraction studies. Results from single-crystal XRD using crystals less than 10 μm in size may rival those obtained from powder diffraction.

Site-selective spectroscopy of Er3+ and Er3+ Yb3+ doped stoichiometric and congruent lithium niobate

In the present work, the optical properties of Er and Er/Yb doped stoichiometric and congruent lithium niobate crystals have been investigated. Low temperature (LHeT) absorption spectra show the appearance of at least six non-equivalent optical centres, with similar structure in Er and Er/Yb co-doped congruent and stoichiometric crystals. In Er/Yb co-doped crystals new centres are also detected. Site-selective spectroscopy reveals differences in up-conversion efficiency and lifetimes between the different centres. An efficient energy transfer from Yb3+ to Er3+ is observed after Yb3+ pumping. Using the rate equations formalism it is shown that population inversion of the Er3+ uper laser level is attainable at sufficiently low pumping levels, making this material suitable for laser applications.

Comparison of electro-optic effect between stoichiometricand congruent LiNbO 3

Comparison of the electro-optic (EO) effect between stoichiometric and congruent lithium niobate (LiNbO3) crystals has been investigated using the Mach-Zehnder interferometer at 0.633 µm wavelength. Anisotropic changes of EO coefficients, r33 and r13, have been found between the stoichiometric and congruent LiNbO3 crystals. The measured r33 value in the stoichiometric LiNbO3 is at least 20% larger than that of LiNbO3 with congruent composition, whereas the r13 coefficient of stoichiometric LiNbO3 is the same as that of congruent LiNbO3.

Sum-frequency generation of continuous-wave sodium D_2 resonance radiation

Sum-frequency generation utilizing two cw single-mode Nd:YAG lasers and a congruent lithium niobate crystal yielded 3.4 mW of very narrow-band (10 kHz over 1 ms) tunable 589-nm cw radiation. This simple solid-state light source is well suited for high-resolution spectroscopy of the sodium D(2) line, as was demonstrated with both conventional and FM-modulated saturation spectroscopy.

Ion beam channeling and hyperfine interaction analysis for the characterization of stoichiometry and anti-site population in LiNbO 3

Combined high precision RBS/channeling, NRA/channeling and perturbed angular correlation studies were used to characterize near-stoichiometric and congruent LiNbO 3 crystals. In congruent LiNbO 3 two non-equivalent Li sites are distinguished whereas in near-stoichiometric LiNbO 3 only one of them exists. A comparison of the experimental results with Monte Carlo simulations was performed to check the validity of the different models for the structure of congruent lithium niobate crystals.

Crystallography of surface nucleation and epitaxial growth of lithium triniobate on congruent lithium niobate

The decomposition of congruent lithium niobate (LN) crystals proceeds by surface nucleation and growth of LiNb3O8 precipitates which exhibit an epitaxial orientation relationship. The same orientation relationship is observed on x-, y-, and z-cut LN substrates. The epitaxy arises from similarities between the two crystal structures and provides for an essentially continuous oxygen-ion framework from parent to product. On y-cut LN, the precipitates have a well-defined habit plane, and the interfacial misfit between the two structures is accommodated by a rectangular grid of misfit dislocations. The density, geometry, and imaging behavior of the misfit dislocations suggest that their Burgers vectors serve to accommodate the disregistry in the oxygen-ion framework. Based on these observations, it is concluded that the mechanism of formation of LiNb3O8 consists of preferential nucleation on the surface and subsequent growth, possibly by counterdiffusion of cations in a closed system where the oxygen-ion framework remains essentially fixed in space.

Low-symmetry Fe-Mg complexes in LiNbO3:Mg

Abstract Congruent lithium niobate crystals doped with Mg and Fe are investigated by means of nuclear magnetic and electron paramagnetic resonances (NMR and EPR), X-ray structure and fluorescence analyses. It is shown that the low-symmetry complexes FeNb-MgLi are created at magnesium concentration above 4.5 mol.%.

Stoichiometry and point defects in lithium niobate crystals

AbstractInvestigations of the OH− ion incorporation into LiNbO3 crystals and the comparison of calculated and measured densities show that undoped congruent lithium niobate crystals contain Li+ and O− − ion vavancies O and Li+. If really present, stacking faults are of inferior importance. The good agreement of the absorption edges of stoichiometric and of 2.7 mol% MgO containing congruent lithium niobate crystals is explained by the occupance of all oxygen sites within these crystals.