B. V. Tatarintsev

The origin of electrooptical sensitivity of glassy materials: crystal motifs in glasses

Abstract The results of studying electrooptical Kerr sensitivity in heavy metal silicate and phosphate glasses and glass-ceramics are presented. A niobium–lithium-silicate glass demonstrating a record Kerr coefficient (266×10−16 m/V2) has been formed. Formation of the transparent glass-ceramics containing electrooptical sodium niobate microcrystals has been studied, and glass-ceramics demonstrating Kerr coefficients higher than 6000×10−16 m/V2 have been elaborated. On the base of the effective medium approximation, it is shown that the Kerr coefficient of these glass-ceramics depends on the volume fraction of sodium niobate microcrystals, vc as a linear function of vc(1−vc)−2 A conception of the origin of electrooptical sensitivity of glasses is proposed. This conception is based on the hypothesis that in glasses there exist regions with exactly crystalline ordering within 2–3 coordination spheres, with these regions having no phase boundaries. These regions are named the crystal motifs (CM). Due to the highly effective mechanism of nuclear polarizability of the electrooptical crystals, the motifs with the symmetry of such crystals are responsible for high permittivity and Kerr sensitivity of the glasses, and they play a role of pre-nuclei while electrooptical glass-ceramics are forming under glass heat treatment. It has been found that synthesized barium-titanate-silicate and niobium–lithium-phosphate glasses demonstrate extremely low Kerr coefficients, and they do not form transparent glass-ceramics with any electrooptical precipitates. This contradicts literature data and is explained by the difference in the conditions of glass synthesis, which are supposed to be responsible for the formation of proper CMs.

Prototype of hybrid diffractive/graded-index splitter for fiber optics

The first example of hybrid diffractive/graded-index optical in- tegration is presented. The demonstrated 1:3 beamsplitter for fiber optics consists of two GRIN lenses and one diffractive element, which are fab- ricated by ion exchange and stacked together to form a solid unit. The unit is coupled with the input optical fiber and with three output ones.

Spectroscopic properties of highly concentrated Nd3-doped antimony-phosphate glass for microchip lasers

The alkaline antimony-phosphate glass doped with Nd3+ was synthesized under different conditions with the controlled content of OH groups. The Nd2O3 concentration varied in the range of 0.2–2.0 mol %; the Sb2O5 concentration was 20 mol %. The absorption and Nd3+ ion luminescence spectra and the absorption spectra of OH groups were obtained. Quenching of the Nd3+ ion luminescence depending on the Nd2O3 and OH group concentrations was studied. It was found that the optimized spectroscopic and kinetic parameters of glass (emission cross section, emission width, radiative lifetime) are close to the parameters of the SCHOTT GLAS industrial laser glass. It was shown that the immediate environment of Nd3+ ions is formed by phosphate polyhedra.

Influence of reduction-oxidation synthesis conditions on the nature of color centers in silicate glass doped with selenium

Silicate glasses doped with elemental selenium and compounds affecting its oxidation state are studied using optical spectroscopy (absorption, resonance Raman scattering, luminescence). The absorption spectra of the synthesized glasses contain three bands with maxima at energies of 1.64, 2.47, and 3.5 eV. The band observed at 2.47 eV is identified in the resonance Raman spectrum from the appearance of the vibrational mode at 323 cm−1, which belongs to the Se2− dimer. The other two bands are supposedly assigned to the Se3− trimer (1.64 eV) and the Se2 dimer (3.5 eV) according to the data available in the literature for the crystal structures. It is shown that the relative content of these centers and their related coloration of glasses are determined by the reduction-oxidation synthesis conditions.

Origin of electrooptical sensitivity of glasses

A niobium-lithium-silicate glass demonstrating a record Kerr coefficient (266•10-16 m/V2) has been formed, and transparent glass-ceramics demonstrating Kerr coefficients exceeding 6000•10-16 m/V2 has been elaborated. A conception of the origin of electrooptical sensitivity of glasses is developed. It supposes that the fluctuation microinhomogeneities peculiar to as-prepared glasses are the regions with exact crystalline symmetry, and that just those regions are the pre-nuclei of the crystallites, which form in glass-ceramics in heat treatment. Having the composition and the symmetry of electrooptical ferroelectric crystal, these regions appear to condition high Kerr sensitivities of both the glasses and the glass-ceramics formed from these glasses.

Influence of diffusion nonlinearity on the characteristics of gradient-index diffractive structures formed in glasses by ion-exchange technique

The influence of the diffusion nonlinearity on the formation of gradient-index diffractive structures by the low-temperature silver ion-exchange method (including electroinduced ion exchange) has been studied for two glasses (light crown type) with the same glass-forming matrix and different alkali compositions. One glass containing only sodium shows the anomalous nonlinearity, and another glass with mixed lithium-sodium composition is characterized by the normal nonlinearity. The silver-sodium exchange in both glasses leads to the same refractive index increments. The simulation of gradient-index diffraction gratings in these glasses demonstrates that the diffusion nonlinearity strongly affects the maximum phase modulations and diffraction efficiency of gradient-index gratings. It is shown that the most efficient diffractive structures can be obtained for glasses with the anomalous diffusion nonlinearity, all other factors being the same.