Temperature dependence of linear electrooptic coefficients r 113 and r 333 in lithium niobate

A new method of determination of individual linear electrooptic coefficients is proposed. The technique is based on the dynamic polarimetric measurements and takes into consideration the temperature dependences of ordinary and extraordinary refractive indices. Results obtained for the electrooptic coefficients r₁₁₃ and r₃₃₃ in LiNbO₃ are presented. The coefficients are found to increase significantly within the considered temperature range 25-200°C. The temperature dependences of the intrinsic coefficients m₁₁₃ and m₃₃₃, defined in terms of the induced polarisation, are considered as well.     

光折变晶体Ce:BaTiO3电光和压电系数的测量

用干涉仪的方法测量了Ce:BaTiO₃晶体的低频电光系数和压电系数．排除压电效应对光通过晶体引起相位的变化，得到低频下经极化的Ce:BaTiO₃单晶的电光系数r₄₂=1945±220pm/V和r₁₃=11.8±1pm/V．从而，为研究Ce:BaTiO₃晶体的光折变效应和理论计算提供了精确的线性电光系数 关键词：     

Synthesis and Characterization of Nonlinear Optical Polymers Containing Carbazole and Disperse Red Dye

Dye‐containing nonlinear optical (NLO) polymers were synthesized: (1) poly(3‐(2‐(3‐(2‐isocyanatopropan‐2‐yl)phenyl)‐2‐methylpropyl)‐4‐methyl‐1‐phenylpyrrolidine‐2,5‐dione), P[(DR1,Cz)MSt‐PMI], and (2) poly(9‐vinyl‐9H‐carbazole‐co‐disperse red 1), PAV[DR1‐Cz]. The synthesized NLO polymers were characterized by ¹H‐NMR, IR, and UV–VIS spectroscopy; differential scanning calorimetry (DSC); and thermogravimetric analysis (TGA). The electro‐optic (EO) coefficients (r₃₃) and their NLO properties were evaluated by simple reflection and the Maker fringe method. The EO coefficients of P[(DR1,Cz)MSt‐PMI] and PAV[DR1‐Cz] were measured at 632.8 nm to be 106 and 46.6 pm/V, respectively. The second harmonic generation (SHG) coefficient (d₃₃) of P[(DR1,Cz)MSt‐PMI] was measured to be 71.25 pm/V.     

Linear and nonlinear optical properties of MgO:LiTaO3

We derive new temperature dependent Sellmeier equations for the extra-ordinary and ordinary refractive indices of 0.5% MgO-doped stoichiometric LiTaO₃ crystal. The equations are based on quasi phase-matched frequency conversion measurements, as well as on interferometric measurements of the thermal expansion and thermal dispersion. These equations fit experimental data over wide spectral ranges: 0.35–6 μm for the extra-ordinary wave and 0.375–3.75 μm for the ordinary wave, from room temperature up to 200°C. The nonlinear optical measurements set lower-limit values for the d ₃₃, d ₂₂, and d ₂₄ elements of the second-order susceptibility tensor χ ⁽²⁾ of 12.9, 1.54, and 0.46 pm/V, respectively. The interferometric measurements enable one to determine the linear and quadratic expansion coefficients of 1.45762e?5 1/°C, and 2.68608e?8 (1/°C)², respectively. The Sellmeier equations are in good agreement with previously published data.     

低阈值极化电压玻璃光波导电光效应的研究

采用热极化技术对掺锗玻璃条形光波导进行极化,通过光纤连接 (单模) 的Mach Zehnder Interferometer 系统测量条形波导内诱导出的电光效应,系统地研究了大气环境下极化条件(极化温度、极化时间、极化电压)对电光效应的影响.结果表明:在最佳极化条件下(406℃、-2.4 kV、20 min),波导内的电光系数为r_TM=0.059±0.001 pm/V, r_TE=0.053±0.001 pm/V,且波导结构中存在一个较低的阈值极化电压(100 V)和阈值极化温度(80℃),此时在波导样品内仍能被激发出可观察的电光效应;实验还发现采用负极化诱导方式产生的电光系数较正极化提高15%左右.     

Electro-optic coefficients of a non-congruent lithium niobate fabricated by vapour transport equilibration: Composition effect

Composition effect on electro-optic (EO) properties of a LiNbO₃ (LN) single-crystal has been investigated in a Li₂O-content range of 47.0–49.95 mol%. Some non-congruent LN crystals with different Li₂O-contents were prepared by performing Li-deficient or Li-rich vapour transport equilibration treatments on as-grown congruent LN crystals. Unclamped EO coefficients γ₁₃ and γ₃₃ of these samples were measured by a Mach–Zehnder interferometric method. The measurements show that in the Li-deficient regime both γ₁₃ and γ₃₃ increase by ～8% as Li₂O-content decreases from the congruent 48.6 mol% to the 47.0 mol% in the Li-deficient regime. The feature is desired for the EO application of the Li-deficient crystal. In the near-stoichiometric regime, both γ₁₃ and γ₃₃ reveal a non-monotonic dependence. As the Li₂O-content increases from the 48.6 mol%, the EO coefficient decreases. Around Li₂O-content 49.5 mol%, a minimum is reached. After that, the EO coefficient recovers slowly. At the stoichiometric composition, it recovers to a value close to that at the congruent point. Comparison shows that different crystal growth methods give rise to different defect structure features and hence different composition effects.     

Metal-insulator transition in Bi-doped,amorphous Ga:Ar mixtures: Influence of spin-orbit scattering

Doping amorphous Ga_xAr_1?x mixtures with the strong spin-orbit scatterer Bi has a dramatic effect on the metal-insulator transition (MIT) occurring in this system at a critical metal atomic concentration x_c: (i) the MIT is shifted from x′_c = 0.36 ± 0.01 (corresponding to a critical metal volume fraction v′_c = 0.19 ± 0.01) of the undoped system to a lower value of x_c = 0.25 ± 0.01 (v_c = 0.14 ± 0.01) for (Ga_0.9Bi_0.1)_xAr_1?x and (ii) the critical exponent v and g of the dc conductivity and Hall coefficient, respectively, change from v′ = 0.5 ± 0.1 and g′ = 0 for the undoped samples to v = 1.3 ± 0.3 and g = 0.5 ± 0.1 for (Ga_0.9Bi_0.1)_xAr_1?x.     

Spatial light manipulation devices using nonlinear polymeric materials

An electrically addressed spatial light modulator with 5 × 5 pixels is designed using nonlinear polymeric materials. Resonator structure for the material is proposed to minimize the driving voltages. Side-chain polymer poly-orange tom-1 isophoronedisocyanate (r ₃₃ = 23 pm/V) is used as a material. A modulation efficiency of 4.7% has been realized with 5.1 V_rms applied voltage at a wavelength of 633 nm. Very fast modulation at over 10 MHz has been demonstrated.     

Measurement of Wavelength Dependence of Electro-Optic Coefficients r22 of Non-doped and 5% MgO-doped Congruent LiNbO3 Crystals and 1.8% MgO-doped Quasi-stoichiometric LiNbO3 Crystal by Multiple Reflection Interference Method

The electro-optic coefficient r ₂₂ in the wavelength range from 409 to 1580 nm was measured for non-doped and 5% MgO-doped congruent LiNbO₃ crystals and 1.8% MgO-doped quasi-stoichiometric LiNbO₃ crystals in a simple optical system using a multiple reflection interference method capable of producing high-precision results without the application of antireflection film to the end faces of the crystal. The influence of the manufacturing errors of the electrooptic crystals was discussed on the measurement of the r ₂₂ coefficient. The experimental errors are less than approximately 0.5% in the wavelength range from 409 to 1064 nm and approximately 1% from 1340 to 1580 nm. It was further shown that polarizing of the laser along X axis resulted in highly accurate measurement of the r ₂₂ of LiNbO₃ crystals.     

Frequency and wavelength dependencies of the electro-optic coefficients in SBN:60 single crystal

We report the dependence of the high and low-frequency values of the linear electro-optic (EO) coefficient r_c=r₃₃-(n_o/n_e)³r₁₃ of Sr_0.6Ba_0.4Nb₂O₆ (SBN:60) single crystal on the laser wavelength. The EO response has been carried out from dc to 150 MHz for four wavelengths ranging from 465 to 1321 nm. The clamped r^S and unclamped r^T coefficients have been determined and their dispersions as a function of wavelength have been established and discussed.     

Index of refraction, optical activity and electro-optic coefficient of bismuth titanium oxide (Bi12TiO20)

12 TiO₂₀. The first two can be measured by simple and classical methods, but the coexistence of optical activity, electrogyration, field-induced linear birefringence, and piezoelectric and photoelastic effects in photorefractive materials such as Bi₁₂TiO₂₀ complicate the measurement of the electro-optic coefficient. For normal incidence of linearly polarized light we derive analytic expressions for the polarization of light that has passed through the crystal. The ellipticity of the polarization is a function of the electric-field-induced linear birefringence and hence of the electro-optic coefficient of the crystal. Therefore measurement of the ellipticity as a function of an electric field externally applied to the crystal leads to an electro-optic coefficient r₄₁ of 5.3±0.1 pm/V. Received: 22 December 1996/Revised version: 21 March 1997     

Structural and physical properties of undoped and nickel-doped BaFe2-xNixAs2（x = 0,0.04） single crystals

<正>Single crystals of undoped and nickel-doped BaFe_(2-x)Ni_xAs_2(x=0,0.04) have been grown by FeAs self-flux method.The maximum dimension of the crystal is as large as ~ 1 cm along the ab plane.The crystalline topography of a cleaved crystal surface is examined by scanning electron microscope(SEM).By x-ray powder diffraction(XRD) experiments using pure silicon as an internal standard,precise unit cell parameters(tetragonal at room temperature) are determined:a = 3.9606(4) A(1 A=0.1 nm),c = 13.015(2) A for BaFe_(1.96)Ni_(0.04)As_2 and a = 3.9590(5) A,c = 13.024(1) A for BaFe_2As_2.DC magnetization and transport measurements are performed to check superconducting transition(T_c=15 K for x=0.04) and other subtle anomalies.For BaFe_(0.96)Ni_(0.04)As_2 crystal,the resistance curve at normal state shows two distinct anomalies associated with spin and structure transitions,and its magnetization data above ~ 91 K exhibit a linear temperature dependence due to spin density wave(SDW) instability.     

Characterization of second and third order optical nonlinearities of ZnO sputtered films

We measured the second and third order optical nonlinearity of zinc oxide, grown on glass substrates by the ion beam sputtering technique. Second and third harmonic generation measurements were performed by means of the rotational Maker fringes technique for different polarization configurations, thus allowing the determination of all non-zero components of the second order susceptibility at three different fundamental beam wavelengths, i.e., 1064 nm, 1542 nm and 1907 nm. The dispersion of the nonlinear optical coefficients has been evaluated, while the nonlinear optical coefficients were found to range between 0.9 pm/V and 0.16 pm/V for d₃₃, 0.53 pm/V and 0.08 pm/V for |d₁₅|, 0.31 and 0.08 pm/V for |d₃₁|, with increasing wavelength. Finally, one third order susceptibility, χ_ijkl ⁽³⁾, has been determined by third harmonic generation measurements at a fundamental wavelength λ=1907 nm and a value for χ₃₃₃₃ ⁽³⁾ of 185×10^-20 m²/V² has been found. PACS 42.65.An; 42.65.Ky; 42.70.Nq     

High pressure X-ray diffraction study on BaWO4-II

BaWO₄-II has been synthesized at 5 GPa and 610°C. Its high pressure behavior was studied by in situ synchrotron X-ray diffraction measurements at room temperature up to 17 GPa. BaWO₄-II retains its monoclinic structure. Bulk and axial moduli determined by fitting a third-order Birch–Murnaghan equation of state to lattice parameters are: K ₀=86.2±1.9 GPa, K ₀(a)=56.0±0.9 GPa, K ₀(b)=85.3±2.4 GPa, and K ₀(c)=146.1±3.2 GPa with a fixed K′=4. Analysis of axial compressible modulus shows that the a-axis is 2.61 times more compressible than the c-axis and 1.71 times more compressible than the b-axis. The beta angle decreases smoothly between room pressure and 17 GPa from 93.78° to 90.90°.     

A holographic method for the determination of all linear electrooptic coefficients applied to Ce-doped strontium-barium-niobate

Using c- and a-cut plates of strontium-barium-niobate doped with 0.66 mol.% cerium all nonzero components of the linear electrooptic tensor r₁₃, r₄₂, r₃₃ including the sign are determined from angular dependence of the two-beam coupling coefficient Γ using transmission and reflection geometry of holographic recording. We found: r₁₃=56 pm/V, r₄₂=38 pm/V, and r₃₃=333 pm/V. In addition we calculated the effective trap density N_eff to be 2.2×10¹⁷ cm^-3. The advantages of this method as well as the values obtained are discussed. Received: 19 November 1998 / Revised version: 15 January 1999 / Published online: 7 April 1999     

Investigation of the resistive transition of CaLaBaCu3O7 in magnetic fields up to 10 tesla and pressures up to 46 GPa

Abstract

The onset critical temperature T _co, of CaLaBaCu₃O₇, is measured as a function of pressure by means of a cryogenic diamond anvil cell. We find ?T _co/?p = 0.14 ± 0.02K/GPa. The pressure dependence of the upper critical field B _c2 as a function of pressure is determined for T/T_c , = 0.96. From this we found the corresponding volume dependence of the number of charge carriers to be much smaller than the value derived from Hall effect measurements in YBa₂Cu₃O₇.

Les dérivées par rapport à la pression de la température critique supérieure T_co , (avec ?T _co,??p = 0.14 ± 0.02K/GPa) et du champs critique B _c2 à T/T_c , = 0.96 ont été déterminé á l'aide d'une presse à diamants. Pour le composé CaLaBaCu₃O₇, la variation de la densité de charges en fonction du volume est beaucoup plus faible que celle détermiée par effet Hall dans YBa₂Cu₃O₇.     

High-frequency response and wavelength dispersion of the linear electro-optic effect in PZN-PT (88/12) single crystal

We have characterized the wavelength dispersion of the high- and low-frequency values of the linear electro-optic coefficient r _c = r ₃₃–(n _o/n _e)³ r ₁₃ of poled 0.88 Pb(Zn_1/3Nb_2/3)O₃–0.12 PbTiO₃ single crystal. The measurements have been investigated as a function of the laser wavelength from 0.465 to 1.32 m. Clamped r ^S and unclamped r ^T values of the electro-optic coefficient as well as the acoustic contribution r ^a have been established. We obtained a ratio of r ^S/r ^T = 30%, which is independent of the wavelength of the light beam. The value of r ^S _c at the wavelength of 633 nm was found to be equal to 50±5 pm/V, which is a rather high value.This revised version was published online in March 2005. In the previous version, the published online date was missing     

High Temperature Diffusion of 6Li Adsorbed on a Ru(001) Single Crystal Surface as Seen by Pulse NMR

Diffusion measurements on lithium atoms adsorbed on a ruthenium single crystal were performed in the high temperature regime (1100–1200 K). Pulsed NMR techniques were utilized to produce and observe the decay of magnetization patterns from which the diffusion coefficient was extracted. The observed temperature dependence could be described by D = (10 ± 7) cm²/s · exp (−(0.46 ± 0.07) eV/kT). The extremely high diffusion coefficient and prefactor are understood by a gas like adsorbate behavior. The electric field gradient has been measured with ⁷Li: V _zz = −5.0 ± 0.1 10¹⁵ V/cm² with an inhomogeneity of less then 1% as judged by the width of the satellite transitions.     

Synthesis and characterization of a family of layered trichalcogenides for assisted hydrogen photogeneration

Three layered trisulfides (TiS₃, ZrS₃, HfS₃) have been synthesized by solid–gas reaction between metal and sulfur in a vacuum sealed ampoule at 550 °C during 60 h. The samples used in this work were prepared from a colloidal suspension of powder of each one of the metal trisulfides (MS₃, M = Ti, Zr, Hf) in ethanol and deposited on titanium disks and quartz substrates by ”drop coating” technique. These samples have been characterized by X‐ray diffraction, energy dispersive analysis of X‐ray and scanning electron microscopy. The obtained direct optical band gaps are 1.0 ± 0.1 eV, 2.0 ± 0.1 eV and 2.2 ± 0.1 eV for TiS₃, ZrS₃ and HfS₃, respectively. Photoelectrochemical measurements in 0.5 M Na₂SO₃ have been carried out to characterize the MS₃/electrolyte interface. The flat‐band potentials (V_fb) vs. Ag/AgCl measured by electrochemical impedance spectroscopy (EIS) are –0.84 ± 0.02 V (TiS₃), –0.93 ± 0.02 V (ZrS₃) and –0.92 ± 0.02 V (HfS₃). Hydrogen generation was investigated in a photoelectrochemical cell (PEC) with MS₃ as photoanodes under white light illumination of 200 ± 20 mW/cm² at external bias potentials of 0.3 V vs. Ag/AgCl. Hydrogen evolution flows have been quantified by quadrupole mass spectrometry (QMS) reaching instantaneous values up to 19 ± 2 nmol H₂/min cm² with TiS₃ as photoanode.     

Ferroelectric phase transition in Cs3Bi2I9

Single crystals of Cs₃Bi₂I₉ have been grown. Polarized-optical, dielectric, and calorimetric studies have been performed, along with measurements of birefringence, and the coefficients of elasticity c ₄₄, and linear expansion a over a wide temperature range. It is found that an intrinsic (pseudo-intrinsic) second-order phase transition to the ferroelastic phase takes place at T ₀=220.0±0.6 K accompanied by a change of the crystal symmetry from 6/mmc to 2/m. The transition parameter depends linearly on the shear strain x ₅ and varies with temperature according to a power law with exponent β=0.5. Zh. éksp. Teor. Fiz. 39, 1850–1852 (October 1997)