Search results for "Tantalate"
showing 10 items of 37 documents
Formation of Layers of Diverse Stoichiometric and Phase Composition in Lithium Tantalate Crystals at Treatment by Vapour Transport Equilibration
2012
Layers from tens to hundreds of microns thick of a different phase composition and stoichiometry are shown to form in lithium tantalate crystals subjected to treatment by vapor transport equilibration in lithium vapour. The 500 microns thick stoichiometric (Li/Ta ≈ 1) layers have ten times lower values of the coercive field compared with congruent lithium tantalate. As electrical measurements suggest, a new polar structure of phase transition at ∼120°C is possibly formed within a thin (30 μm) surface layer of the lithium tantalate sample after vapour transport equilibration treatment.
Depolarization Currents and Ageing in Layered Na0.5Bi8.5Ti2Nb4O27and Na0.5Bi8.5Ti2Ta4O27Ferroelectrics
2009
The present study is focused on the behaviour of polarization and depolarization currents and processes of the slow relaxation of polarization within the range of temperatures where the anomalies are displayed by the materials. Results of the study are discussed with regard to possible existence of defect complexes in disordered ferroelectrics.
Isomorphous ion substitutions and order-disorder phenomena in highly electrocaloric lead-scandium tantalate solid solutions
1996
Abstract The authors discuss the physical background of the electrocaloric effect in PST ceramics and its solid solutions. The most important contribution to the electrocaloric effect is due to field-induced Fm3m→R3m phase transition in the case of high long range ordering degree of B-ions in the perovskite structure ABO3.
Random quasi-phase-matched second-harmonic generation in periodically poled lithium tantalate
2010
We observe second harmonic generation via random quasi-phase-matching in a 2.0 micron periodically poled, 1-cm-long, z-cut lithium tantalate. Away from resonance, the harmonic output profiles exhibit a characteristic pattern stemming from a stochastic domain distribution and a quadratic growth with the fundamental excitation, as well as a broadband spectral response. The results are in good agreement with a simple model and numerical simulations in the undepleted regime, assuming an anisotropic spread of the random nonlinear component. (C) 2010 Optical Society of America
Broadband Second-Harmonic Generation via Random Quasi-Phase-Matching in PPLT
2010
We demonstrated broadband second-harmonic generation via random Quasi-Phase-Matching in periodically poled Lithium Tantalate.
Quantum chemical calculations of KTN solid solutions
1998
Abstract The results of semi-empirical calculations for perovskite KNbxTa1−xO3 (KTN) solid solutions are presented for x = 0.04, 0.11, 0.89, and 0.96. Quantum chemical method of the Intermediate Neglect of the Differential Overlap (INDO) was combined with 135- and 320-atom supercells. Analysis of the optimised atomic and electronic structure has clearly demonstrated that several nearest Nb atoms substituting for Ta in KTaO3 — unlike Ta impurities in KNbO3 — reveal the self-ordering effect, which probably triggers the ferroelectricity observed in KTN.
Integrated frequency shifter in periodically poled lithium tantalate waveguide
2010
A frequency shifting device is fabricated and tested in a ferroelectric waveguide in a low-photorefractivity crystal. Periodic poling for quasi-phase-matching and channels for operation in the near-infrared C-band were obtained in congruent lithium tantalate, demonstrating for the first time both wave confinement and two-stage parametric conversion in such waveguides.
Random quasi-phase matching in congruent lithium tantalate waveguides by proton exchange
2012
A report is presented on broadband second-harmonic generation in the range between 930 and 970 nm using random quasi-phase matching in a planar waveguide fabricated by soft proton exchange in congruent lithium tantalate. Bulk and waveguide measurements are compared, outlining the averaging role of guided-wave modes and their interactions with respect to spectral acceptance and near-field profile.
Second Harmonic Generation via Random Quasi-phase Matching in a Periodically Poled Lithium Tantalate Waveguide
2011
We observe second harmonic generation via random quasi phase matching in a 1.5μm periodically poled lithium tantalate. The presence of a slab waveguide allows the comparison between bulk and guided wave configurations.
GENERAZIONE DI SECONDA ARMONICA IN GUIDA D’ONDA IN TANTALATO DI LITIO CONGRUENTE CON POLING PERIODICO E CONVERSIONE DI LUNGHEZZA D’ONDA IN BANDA C + L
2010
Here we show the results obtained by the characterization of a lithium-tantalate based device for second-harmonic-generation and all-optical wavelength conversion. The waveguides have been obtained by proton-exchange in a periodically-poled congruent lithium tantalate substrate.