Noncritical phase-matched second harmonic generation was measured in optically biaxial KNb(1-x)Ta(x)O3 mixed crystals in the orthorhombic phase. For Nd:YAG-(1064 nm) the coefficient d31 of the tensor of the nonlinear susceptibility was applied, while for the GaAs-laser (905 nm) the coefficient d32 was used. For both laser wavelengths the phase-matching temperature decreases with increasing Ta concentration. Noncritical phase-matching at room temperature can be reached with the GaAs-laser for a Ta concentration of almost-equal-to 9%. The corresponding value for the Nd:YAG laser is almost-equal-to 14%.

Noncritical phase-matched second harmonic generation was measured in optically biaxial KNb1−xTaxO3 mixed crystals in the orthorhombic phase. For Nd:YAG-(1064 nm) the coefficient d31 of the tensor of the nonlinear susceptibility was applied, while for the GaAs-laser (905 nm) the coefficient d32 was used. For both laser wavelengths the phase-matching temperature decreases with increasing Ta-concentration. Noncritical phase-matching at room temperature can be reached with the GaAs-laser for a Ta concentration of ≊9%. The corresponding value for the Nd:YAG laser is ≊14%.

For KNb1-xTaxO3 crystals the influence of the Ta-concentration on the phase-matching properties for optical second harmonic generation (SHG) was measured. For non-critical phase matched SHG of the Nd:YAG-laser (1064nm) the coefficient d31 of the tensor of the nonlinear susceptibility was applied, while for the GaAs-laser (905 nm) the coefficient d32 was used. For both laser wavelengths the phase-matching temperature decreases with increasing Ta-concentration. Non-critical phase-matching at room temperature can be reached with the GaAs-laser for a Ta-concentration of ≈9%. The corresponding value for the Nd:YAG-laser is ≈14%.

Single crystals of K(Ta1-xNbx)O3 with compositions 0.30

Single crystals of K(Ta 1− x Nb x )O 3 with compositions 0.35 ⩽ x ⩽ 1 have been grown from a solution of molten KNbO 3 + KTaO 3 with an excess of K 2 O. In order to minimize variations in the Nb/Ta ratio, a method was developed to grow crystals at a small temperature gradient and at a low growth rate. To characterize the homogeneity of the crystals, the spatial fluctuations of the Nb/Ta ratio were resolved by electron microprobe analysis. The temperature dependence of the dielectric constant of the whole crystals was measured. The results indicate that the spatial variation of the Nb/Ta ratio cannot explain the dielectric behavior. We suppose that internal stress, caused by the tendency of exsolution in the system KNbO 3 - KTaO 3 , must be taken into consideration.

Undoped single crystals of KTaO3 grown in our crystal growth laboratory show only one isotropic absorption line which is due to an OH stretch mode. Conflicting results with more than one mode have been reported so far. A well resolvable splitting is observed for an electric field applied perpendicular to the light propagation. From the overtone and the corresponding frequencies of the deuteron isotope, the spectroscopic parameters for an anharmonic oscillator are deduced. Right angle Raman scattering yield the Raman tensor of the dipole ensemble and point to an almost undisturbed charge distribution, when compared with the free OH molecule.

Using ESR, the authors identified Fe3+ in the rhombohedral phase of the photorefractive compound KNbO3. Fe3+-Vo was found in the orthorhombic as well as the rhombohedral phases. The spectra were analysed and compared to those of Fe3+ and Fe3+-Vo in other oxide compounds, e.g. BaTiO3. A superposition model analysis yielded information on the geometry of Fe3+ and its nearest neighbours. Also Co2+, Co2+-Vo and Ir4+ were identified, analysed and compared to corresponding findings in other oxide hosts.

physica status solidi (a)Volume 116, Issue 2 p. K195-K198 Short Note The influence of stress on the dielectric properties of KTN crystals F. Baller, F. Baller FB Physik und FB Biologie/Chemie der Universität Osnabrück Search for more papers by this authorB. Gather, B. Gather FB Physik und FB Biologie/Chemie der Universität Osnabrück Search for more papers by this authorB. Hellermann, B. Hellermann FB Physik und FB Biologie/Chemie der Universität Osnabrück Search for more papers by this authorH. Hesse, H. Hesse FB Physik und FB Biologie/Chemie der Universität Osnabrück Search for more papers by this authorE. Krätzig, E. Krätzig FB Physik und FB Biologie/Chemie der Universität Osnabrück Search for more papers by this author F. Baller, F. Baller FB Physik und FB Biologie/Chemie der Universität Osnabrück Search for more papers by this authorB. Gather, B. Gather FB Physik und FB Biologie/Chemie der Universität Osnabrück Search for more papers by this authorB. Hellermann, B. Hellermann FB Physik und FB Biologie/Chemie der Universität Osnabrück Search for more papers by this authorH. Hesse, H. Hesse FB Physik und FB Biologie/Chemie der Universität Osnabrück Search for more papers by this authorE. Krätzig, E. Krätzig FB Physik und FB Biologie/Chemie der Universität Osnabrück Search for more papers by this author First published: 16 December 1989 https://doi.org/10.1002/pssa.2211160259Citations: 10 Barbarastr. 7, D-4500 Osnabrück, FRG. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL References 1 F. S. Chen, J. E. Gensic, S. K. Kurtz, J. G. Skinner, and S. H. Wemple, J. appl. Phys. 37, 388 (1966). 2 A. J. Fox and P. W. Whipps, Electronics Letters 7, 139 (1971). 3 F. S. Chen, J. appl. Phys. 38, 3418 (1967). 4 D. Von Der Linde, A. M. Glass, and K. F. Rodgers, Appl. Phys. Letters 26, 155 (1975). 5 L. A. Boatner, E. Krätzig, and R. Orlowski, Ferroelectrics 27, 247 (1980). 6 S. Triebwasser, Phys. Rev. 114, 63 (1959). 7 R. Reisman and F. Holtzberg, J. Amer. Chem. Soc. 77, 2115 (1955). Citing Literature Volume116, Issue216 December 1989Pages K195-K198 ReferencesRelatedInformation

Under illumination with visible and near UV light, Ti doped KNbO3 shows ESR of O- trapped holes as well as a corresponding optical absorption band with maximum at ∼ 2 eV. In the most likely model the hole wavefunction extends over two neighbouring oxygen ions next to Ti4+ substituting for Nb5+.

In a KNbO3 single domain substrate crystal a permanent multimode waveguide has been produced for the first time by implantation of 2 MeV He+ ions. Annealing is unnecessary since electronic damage is small. The irradiation flux was controlled such that no unwanted phase transitions or domain formation occured. The refractive index profile was investigated by dark line mode spectroscopy and reconstructed by a new inverse WKB procedure. The waveguiding layer has a thickness of about 3 μm, in the region directly below this layer the refractive index is decreased by more than 0.1.

By calculating the potential distribution in ferroelectric crystals with applied electric field it is shown that—depending on the domain geometry—large field distortions occur which are due to the anisotropy of the dielectric susceptibility in ferroelectrics. These distortions can explain many of the problems showing up when poling crystals by an electric field.