A. Majchrowski

CsLiB6O10 crystallites embedded into olygoether photopolymer matrices as new materials for acoustically induced nonlinear optics

Abstract Acoustically induced optical second harmonic generation (SHG) in CsLiB6O10 (CLBO) nanocrystallites incorporated into the olygoether photopolymer matrices has been revealed at liquid helium temperature (4.2 K). The SHG has been measured for the source wavelength of an YAG-Nd laser (λ=1.06 μm ) . With increasing acoustical power, the SHG signal increases and achieves its maximum at acoustical intensity of about 18.1 W/cm2 and frequency of about 14 kHz. The value of the SHG χ222 tensor component was comparable with the one for the traditional nonlinear optical crystals such as KH2PO4, KTiOPO4, LiNbO3. With decreasing temperature (below 28 K) the acoustically induced SHG signal strongly increases. A correlation between the acoustically nonlinear optical response and low-frequency Raman intensities has been found. The maximal acoustically induced SHG has been observed for the nanocrystallite concentration of about 3.1% (in weight units) and the nanocrystallite sizes lying within 35–40 nm. The SHG tensor coefficients were larger than for the bulk CLBO crystals (at least 13%). Advantages and drawbacks of the presented model are discussed. The theory of the observed phenomena is explained on the grounds of the ab initio band energy calculations with taking into account anharmonic electron–phonon interactions.

Effect of U on the Electronic Properties of Neodymium Gallate (NdGaO3): Theoretical and Experimental Studies

We have performed a density functional calculation for the centrosymmetric neodymium gallate using a full-potential linear augmented plane wave method with the LDA and LDA+U exchange correlation. In particular, we explored the influence of U on the band dispersion and optical transitions. Our calculations show that U = 0.55 Ry gives the best agreement with our ellipsometry data taken in the VUV spectral range with a synchrotron source. Our LDA+U (U = 0.55) calculation shows that the valence band maximum (VBM) is located at T and the conduction band minimum (CBM) is located at the center of the Brillouin zone, resulting in a wide indirect energy band gap of about 3.8 eV in excellent agreement with our experiment. The partial density of states show that the upper valence band originates predominantly from Nd-f and O-p states, with a small admixture of Nd-s/p and Ga-p B-p states, while the lower conduction band prevailingly originates from the Nd-f and Nd-d terms with a small contribution of O-p-Ga-s/p states. The Nd-f states in the upper valence band and lower conduction band have a significant influence on the energy band gap dispersion which is illustrated by our calculations. The calculated frequency dependent optical properties show a small positive uniaxial anisotropy.

Growth and properties of potassium holmium double tungstate KHo(WO4)2

Potassium holmium tungstate KHo(WO 4 ) 2 crystal, as other tungstates, shows the high temperature irreversible structural phase transition. Owing to this, KHo(WO 4 ) 2 single crystals were grown due to spontaneous crystallisation with use of the High Temperature Solution Growth technique, which allows to lower the temperature of crystallisation below the temperature of the phase transition. K 2 W 2 O 7 was used as a solvent. It provides a very wide temperature range of crystallisation and does not introduce additional impurities into the melt. The starting flux contained 20 mol% of KHo(WO 4 ) 2 dissolved in K 2 W 2 O 7 . It was found that potassium holmium double tungstate is pleochroic. The two different optical spectra: one spectrum for electrical vector of linearly polarised light parallel to optical Y axis (main spectrum) and second one for electrical vector perpendicular to Y axis were measured.

Optical transitions of Pr3+ ions in Ca4GdO(BO3)3 crystals

Abstract Optical properties of Pr 3+ ions in gadolinium calcium oxoborate Ca 4 GdO(BO 3 ) 3 (GdCOB) nonlinear crystals have been studied. Polarized absorption and emission spectra and fluorescence lifetime measurements have been performed and discussed using modified Judd-Ofelt theory. The system is characterized by intense red emission at 610 nm corresponding to the 1 D 2 → 3 H 4 transition, no emission from the excited 3 P 0 state has been observed. 1 D 2 emission has been investigated under pulsed excitation and the experimental lifetimes for this level has been compared with this obtained theoretically by using Judd–Ofelt approach.

Optical properties of KGd(WO4)2 single crystals studied by Brillouin spectroscopy

The analysis some of the acoustic phonons propagating in pure and Ho3+-doped KGd(WO4)2 single crystals in the GHz frequency range by Brillouin scattering method has been presented. For investigated crystals the velocities of the longitudinal and transverse acoustic phonons [100], [010], [001], [101], [101] and [110] have been determined. Moreover, the value of elastic constants C22, C44 and C66 of pure and Ho3+-doped KGd(WO4)2 single crystals have been estimated. It was revealed that the presence of the Ho3+-ions in KGd(WO4)2 crystals, for the used doping concentration 1 at% and 8 at%, does not influence their elastic properties. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Influence of the rare-earth doping on the photoinduced EOEs in the GdCOB

Abstract We have discovered a photoinduced linear electrooptics effect (EOE) in the GdCOB doped by the rare earth ions of Tm 3+ and Sm 3+ . We have found that doping by Tm 3+ is essentially more efficient for increasing EOE compared with the Sm 3+ ones. Moreover, increasing the Sm 3+ content diminishes the values of the r 23 electrooptics coefficient. For comparison, the corresponding values for the pure GdCOB are non-sensitive to UV pumping power and maximal EOE is less than 0.3 pm/V.

Comparison of the Density of States Obtained from the X-ray Photoelectron Spectra with the Electronic Structure Calculations for α-BiB3O6

We report measurements of the X-ray photoelectron spectrum on single crystals of α-BiB3O6. We also present first principles calculations of the band structure and density of states using the full potential augmented plane wave method. In this paper we make a detailed comparison of the density of states deduced from the X-ray photoelectron spectra with our calculations. We find that the valence band maximum (VB) is located at M symmetry point, while and the conduction band minimum is around half way between the symmetry points Z and Γ resulting in an indirect energy gap of 4.1 eV compared to our measured experimental value of 4.55 eV. The theoretical results of the density of states are in reasonable agreement with the X-ray photoelectron spectroscopy (VB-XPS) measurements with respect to peak positions. We have analyzed the calculated density of states and find a strong/weak hybridization between the B, O, and Bi states in the valence and conduction bands.

Optical second harmonic generation in Yttrium Aluminum Borate single crystals (theoretical simulation and experiment)

Experimental measurements of the second order susceptibilities for the second harmonic generation are reported for YAl3(BO3)4 (YAB) single crystals for the two principal tensor components xyz and yyy. First principles calculation of the linear and nonlinear optical susceptibilities for Yttrium Aluminum Borate YAl3(BO3)4 (YAB) crystal have been carried out within a framework of the full-potential linear augmented plane wave (FP-LAPW) method. Our calculations show a large anisotropy of the linear and nonlinear optical susceptibilities. The observed dependences of the second order susceptibilities for the static frequency limit and for the frequency may be a consequence of different contribution of electron-phonon interactions. The imaginary parts of the second order SHG susceptibility χ123(2)(ω)MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8bkY=wiFfYlOipiY=Hhbbf9v8qqaqFr0xc9vqpe0di9q8qqpG0dHiVcFbIOFHK8Feei0lXdar=Jb9qqFfeaYRXxe9vr0=vr0=LqpWqaaeaabiGaciaacaqabeaabeqacmaaaOqaaiabeE8aJnaaDaaaleaacqaIXaqmcqaIYaGmcqaIZaWmaeaacqGGOaakcqaIYaGmcqGGPaqkaaGcdaqadaqaaiabeM8a3bGaayjkaiaawMcaaaaa@35B5@, χ112(2)(ω)MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8bkY=wiFfYlOipiY=Hhbbf9v8qqaqFr0xc9vqpe0di9q8qqpG0dHiVcFbIOFHK8Feei0lXdar=Jb9qqFfeaYRXxe9vr0=vr0=LqpWqaaeaabiGaciaacaqabeaabeqacmaaaOqaaiabeE8aJnaaDaaaleaacqaIXaqmcqaIXaqmcqaIYaGmaeaacqGGOaakcqaIYaGmcqGGPaqkaaGcdaqadaqaaiabeM8a3bGaayjkaiaawMcaaaaa@35B1@, χ222(2)(ω)MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8bkY=wiFfYlOipiY=Hhbbf9v8qqaqFr0xc9vqpe0di9q8qqpG0dHiVcFbIOFHK8Feei0lXdar=Jb9qqFfeaYRXxe9vr0=vr0=LqpWqaaeaabiGaciaacaqabeaabeqacmaaaOqaaiabeE8aJnaaDaaaleaacqaIYaGmcqaIYaGmcqaIYaGmaeaacqGGOaakcqaIYaGmcqGGPaqkaaGcdaqadaqaaiabeM8a3bGaayjkaiaawMcaaaaa@35B5@, and χ213(2)(ω)MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8bkY=wiFfYlOipiY=Hhbbf9v8qqaqFr0xc9vqpe0di9q8qqpG0dHiVcFbIOFHK8Feei0lXdar=Jb9qqFfeaYRXxe9vr0=vr0=LqpWqaaeaabiGaciaacaqabeaabeqacmaaaOqaaiabeE8aJnaaDaaaleaacqaIYaGmcqaIXaqmcqaIZaWmaeaacqGGOaakcqaIYaGmcqGGPaqkaaGcdaqadaqaaiabeM8a3bGaayjkaiaawMcaaaaa@35B5@ are evaluated. We find that the 2ω inter-band and intra-band contributions to the real and imaginary parts of χijk(2)(ω)MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbwvMCKfMBHbqedmvETj2BSbqee0evGueE0jxyaibaieYdOi=BI8qipeYdI8qiW7rqqrFfpeea0xe9LqFf0xc9q8qqaqFn0dXdHiVcFbIOFHK8Feei0lXdar=Jb9qqFfeaYRXxe9vr0=vr0=LqpWqaaeaabiGaciaacaqabeaabeqacmaaaOqaaiabeE8aJnaaDaaaleaacaWGPbGaamOAaiaadUgaaeaacaGGOaGaaGOmaiaacMcaaaGcdaqadaqaaiabeM8a3bGaayjkaiaawMcaaaaa@3752@ show opposite signs. The calculated second order susceptibilities are in reasonable good agreement with the experimental measurements.PACS Codes: 71.15. Mb; 71.15.-m

Crystal Growth Of Mixed Titanium Sillenites

(BGaO) single crystals have been grown, oo. Thermal conditions enabling growth oft uniform [110] sillenite single crystals with totally flat (110) interface have been found. Influence of composition on spectral characteristics of the BTO mixed crystals has been investigated. Keywords: sillenites, BTO, top seeded solution growth, optical absorption (Received November 6, 2002; Accepted May 14, 2002)

Pockels effect in yttrium aluminum borate single crystals

Experimental measurements of linear electro-optical coefficients are reported for YAl3(BO3)4 (YAB) single crystals for the two principal tensor components xyz and yyy at the wavelength of a CW semiconducting GaAlAs laser emitting at 1040 nm. We have found the values of the Pockels coefficients to be equal to 0.21 ± 0.06 and 0.56 ± 0.08 pm/V for 123 and 222 Pockels components, respectively. Additional measurements performed for the thin-cut samples with the thickness varying within the 100–500 μm have confirmed the values of the corresponding parameters. We have eliminated a contribution of the piezooptical coefficients as well as for other disturbing factors. We have established that the crystals with a different number of defects do not show any differences, which indicate the principal role of the borate clusters on the observed effects. The temperature changes are very low (due to a low ionic contribution), and do not exceed 5–6%, which indicates the low contribution of the electron-phonon to the Pockels effect. Because the YAB crystals possess a very large photothermal damage (more than 15 GW/cm2) and are only slightly temperature dependent. Hence, they may be proposed as promising materials for high-power laser electro-optic modulators.