Anomalously Large Pockels Effect in ZnO‐F Single Crystalline Films Deposited on Bare Glass

Large linear electrooptics (the Pockels effect) of up to 17 pm/V for the wavelength 435 nm has been observed in ZnO films doped by fluorine and deposited on bare glass. In order to describe the phenomenon observed, a complex approach, including self‐consistent band structure calculations together with the appropriate molecular dynamics simulations of the interfaces, was applied. The origin of the effect observed is linked to substantial charge density non‐centrosymmetry between the wurtzitelike crystalline films and the bare glass substrate, as well as to additional charge density polarisation caused by the fluorine.     

Photoinduced nonlinear optics methods as new methods of monitoring the superconducting films

A new method of monitoring the superconductivity in the Hg-1201 films is proposed using the photoinduced optical second harmonic generation (PISHG). In the present work the experimental PISHG results are presented for the Hg-1201 films deposited on the MgO substrates. We have found that the PISHG is more sensitive compared with the traditional methods (resistivity, magnetic susceptibility, etc.). Using of the pump–probe technique allows obtaining additional parameters of the carrier relaxation responsible for the superconductivity. The proposed method has an advantage compared with the others because they are contactless and non-invasive and give a possibility to detect the phase transitions with higher precision.     

Surface morphological changes and magnetic properties of Sc-substituted Y3Fe5O12 epitaxial films deposited on the GGG substrate

Sc-doped YIG films were grown on (1 1 1) oriented GGG crystalline substrate with disorientation angle within the range 0-25′. Sc³⁺ ion substitution was varied within the range 0.25-0.3 per formula unit. The films demonstrate different types of surface morphology versus film growth rate and substrate disorientation. Conditions for existence of these types of the surface morphology were defined. The field dependence of magnetic susceptibility at magnetization reversal in film plane and Faraday rotation at wavelength 633 nm for a magnetic field applied in perpendicular direction were measured to characterize the films grown. Films with “mirror-like” surface demonstrate a planar magnetization at room temperature.     

The role of ligand coordination on the spectral features of Yb3+ ions in lead aluminum silicate glasses

The glasses of the composition (40 ? x)PbO–(5 + x)Al₂O₃–54SiO₂:1.0Yb₂O₃ (in mol%) with x ranging from 5 to 10 have been synthesized. The IR spectral studies of these glasses have indicated that there is a gradual transformation of Al³⁺ ions from tetrahedral to octahedral coordination with increase of Al₂O₃ content in the glass network. The optical absorption and luminescence spectra have exhibited bands originating from ²F_7/2 → ²F_5/2 and ²F_5/2 → ²F_7/2 transitions, respectively. From these spectra, the absorption and emission cross-sections and fluorescence lifetime of Yb³⁺ ions have been evaluated. Quantitative analysis of these data indicated a decreasing radiative trapping and increasing fluorescence lifetime of Yb³⁺ ions with increasing Al₂O₃ content. This may be explained by structural variations in the vicinity of Yb³⁺ ions due to variation in the concentration of Al₂O₃ in the glass network.     

Synthesis and characterization of NLO chromophore with benzo [1,2-b:4,5-b′]dithiophene unit as π-electron bridge

A novel chromophore BDT–TCF with benzo[1,2-b:4,5-b′]dithiophene (BDT) unit as electron bridge was synthesized and characterized by UV–vis, NMR spectroscopy, and thermal analysis. It is the first time that BDT unit was introduced into NLO materials. The chromophore showed excellent solubility in most common solvents, and good thermal stability for practical applications. The second order nonlinear optical effect was measured by hyper Rayleigh scattering method. The diagonal hyperpolarizability β_zzz of BDT–TCF was 8.2 × 10^?28 and 9.3 × 10^?29 esu in THF solvent and in PMMA polymer matrices, respectively. The potential NLO response indicates that BDT unit is a promising π-electron bridge and an excellent candidate for nonlinear optical devices.     

DFT/TDDFT Study on the Electronic Structure and Spectral Properties of Diphenyl Azafluoranthene Derivative

Paper reports the DFT/TDDFT study on the electronic structure and spectral properties of the five-membered annulated diphenyl azafluoranthene derivative 1,3-diphenyl-3H-indeno[1,2,3-de]pyrazolo[3,4-b]quinoline (DPIPQ) by means of polarizable continuum model (PCM) and Onsager reaction field approaches at the B3LYP/6-31+G(d,p) level of theory. The results of calculations are compared with the optical absorption and fluorescence spectra as well as with the cyclic voltammetry data. The DFT/TDDFT/PCM approaches exhibit rather good quantitative agreement regarding the spectral position of the first absorption band; the discrepancy between the experiment and theory is less than 0.06 eV (linear response approach) or 0.25 eV (state specific approach). As for the fluorescence emission the TDDFT/PCM calculations underestimate the transition energy on about of 0.7–0.8 eV. Such discrepancy should be attributed to insufficient quality of the TDDFT/PCM optimization in the excited state. Ignoring the geometrical relaxation in the excited state provides considerably better agreement between the experiment and theory; discrepancy is less than 0.1–0.22 eV depending on a solvent polarity. The dominant influence on the fluorescence emission results mainly from the solvent reorganization in the excited state whereas the solute relaxation is indeed weak and may be ignored.     

Influence of valence and coordination of manganese ions on spectral and dielectric features of Na2SO4–B2O3–P2O5 glasses

Sodiumsulpho borophosphate glasses with composition (40 ? x)Na₂SO₄–30B₂O₃–30P₂O₅: xMnO with x ranging from 0 to 5.0 mol% were manufactures. Dielectric spectra have been studied over a wide frequency range of 10²–10⁵ Hz and in the temperature range within 30–250 °C. The valance states of manganese ions and their ligand coordination in the glass network have been investigated using optical absorption, luminescence and ESR spectroscopy. The analysis of the these results has indicated that the manganese ions exist both in Mn²⁺ as well as in Mn³⁺ states and occupy prevailingly octahedral positions and serve as modifiers similarly to Na⁺ ions The values of dielectric parameters (dielectric constant, ε′(ω), loss tan δ and ac conductivity, σ_ac) were found to increase with increasing MnO content. They play a role of modifiers similarly to Na⁺ ions, create bonding defects and free ions viz., [SO₄]^2?, [POO_1/2O₂]^2?, [POO_0/2O₃]^3–, Na⁺ and (NaSO₄)^?. The migration of these charge carriers would build up space charge polarization and may be responsible for the enhanced dielectric parameters. The ac conductivity also is enhanced with increasing MnO content. The mechanism responsible for such increase is well explained based on the modifying action of Mn²⁺ ions.     

PbO–Bi2O3–Ga2O3–BaO glasses doped by Er as novel materials for IR emission

Infra-red luminescence (at wavelengths about 1600 and 2500 nm) from Er³⁺ ions embedded in PbO–Bi₂O₃–Ga₂O₃–BaO glass hosts is reported for room and helium liquid temperatures. The substantial influence of energy transfer processes between the host and Er³⁺ ions is shown experimentally through the dependences of photoluminescence on light polarization and excitation wavelength. Only the application of the polarized pumping YAG–Nd laser beam (λ=1060 nm) stimulates substantial luminescence with quantum efficiency up to 24%. The role of phonon-relaxation subsystem in the observed luminescence is discussed.