Optimum Poling Conditions Research Articles

Matching molecular and optical multipoles in photoisomerizable nonlinear systems

We experimentally investigate the coupling rules between molecules and optical fields in the all-optical poling scheme. The efficiency and symmetry of the photoinduced quadratic nonlinearity is shown to be dependent on tensorial selection rules connecting the symmetries of the optical poling fields and the molecular tensors. We show that an optimal poling is obtained by matching the molecular symmetry to either a quasi-dipolar or a purely octupolar poling field, each being engineered by use of circular polarizations. Moreover, we define optimized poling conditions allowing the direct measurement of molecular nonlinear anisotropies. This research can be applied to nonlinear and photoisomerizable multipolar molecular systems.

Piezoelectric Properties of Sodium Bismuth Tantalate Na0.5Bi2.5Ta2O9 Dense Ceramics

The piezoelectric properties of sodium bismuth tantalate Na0.5Bi2.5Ta2O9 (NBTa) dense ceramics were determined using 0.1 wt% Mn-doped samples. The ferroelectric properties of the NBTa ceramics were confirmed. The remanent polarization Pr and coercive field Ec were 15.5 µC/cm2 and 81.5 kV/cm at room temperature, respectively. Optimum poling conditions (temperature Tp, time tp and electric field Ep) were investigated for piezoelectric measurements. The independent electromechanical coupling factors of the NBTa dense ceramics were obtained as follows: kp=10.0, k31=6.1, k33=12.4 and k15=5.6%. These values are comparable to those of the reported bismuth layer-structured ferroelectrics (BLSFs) that are composed of two pseudo-perovskite layers. The physical constants of the NBTa ceramics were also determined. The piezoelectric constants were d33=10.8, d31=5.2, and d15=6.0 pC/N.

Piezoelectric activity and its stability of polytetrafluoroethylene(PTFE)films

Piezoelectricity of non-polar space charge electret, porous PTFE film with unidi rectional mechanical stretch was studied. Piezoelectricity of double-layer stack s of porous PTFE and non-porous polymer films (such as PTFE, PI, FEP and PCTFE) with space charge layer were investigated. The results of preliminary investigat ion pointed out that under the optimal poling conditions, piezoelectric coeffici ent d33 of porous PTFE with external electrode was up to 186 pC/N whi c h is close to the value of ferroelectric ceramics PZT, and was about one order o f magnitude that of ferroelectric polymer PVDF. Outstanding thermal stability of piezoelectricity for soft PTFE porous film was reported. Influences of poling parameters such as poling time, corona electrical field and charging temperature etc, as well as charge density stored in the material on piezoelectricity were investigated. The influences of charging parameters on piezoelectricity were also explained by means of charge dynamic character and the material property.

Optimization and characterization of the guest-host polyetherketone polymer films for application in integrated optical devices

In order to optimize the loading of 3-(1,1-dicyanothenyl)-1-phenyl-4, 5-dihydro-1H-pryazole (DCNP) in polyetherketone (PEK-c) guest-host polymer films, ten kinds of DCNP/PEK-c thin films, in which the weight per cent of DCNP changes from 5 to 50, were prepared. Their second-order nonlinear optical coefficients χ33(2) at λ = 1064 nm were measured by using Maker fringe method after poling under the optimal poling condition. Their optical waveguide transmission losses were measured at 632.8 nm. Optimal weight per cent of the chromophore for the DCNP/PEK-c guest-host polymer system has been determined as about 20 for use in the integrated optical devices.

Side radical influence on the nonlinear optical properties and thermal stability of poled polymer films

Films of polyetherketone doped with the chromophores Disperse Red 1 (DR1) and Disperse Red 13 (DR13) were prepared by spin-coating method. By the in situ Second-harmonic Generation (SHG) signal intensity measurement, the optimal poling temperatures were obtained. For the investigated polyetherketone polymer doped with DR1 (DR1/PEK-c) and polyetherketone polymer doped with DR13 (DR13/PEK-c) films, the optimal poling temperatures were 150°C and 140°C, respectively. Under the optimal poling conditions, the high second-order nonlinear optical coefficient χ33(2) = 11.02 pm/V has been obtained for the DR1/PEK-c; and for DR13/PEK-c at the same conditions the coefficient is 17.9 pm/V. The SHG signal intensity DR1/PEK-c could maintain more than 80% of its initial value when the temperature was under 100°C, and the SHG signal intensity of the DR13/PEK-c could maintain more than 80% of its initial value when the temperature was under 135°C.

Ca and La-Modified Lead Titanate Sol-Gel Thin Films by UV-Assisted Processing for Piezoelectric Sensors

A diol-based sol-gel method was used to prepare UV sensitive precursor solutions in the processing of modified lead titanate ferroelectric thin films. Films were deposited by spin-coating onto platinized Si-based substrates. A <111> preferential orientation was promoted by appropriated choice of the substrate and multiple deposition and crystallization steps. Processing under UV radiation was carried out in a novel RTP equipment including an arrangement of high intensity UV excimer lamps. To obtain the desired ferroelectric perovskite structure, moderate temperatures and times were required, with respect to those of the processing without UV irradiation. XRD measurements were carried out to determine the degree of orientation of the films. Ferroelectric characterization was made to investigate the optimum poling conditions of the films. Piezoelectric coefficients, e 31 and d 33 , were determined in order to evaluate the feasibility of the use of the films in piezoelectric sensors.

Nonlinear optical (NLO) polymers. IV. Second‐order optical nonlinearity of NLO polyurea and copolyurea with NLO dipole moments aligned transverse to the main backbone

This article presents the molecular orientation and second-order optical nonlinearity of newly prepared polyureas and copolyurea with dipole moments aligned transverse to the main backbone. Nonlinear optical (NLO) polyureas, TPU and TPU2, were prepared from 2,4-diamino-4′-nitroazobenzene (2R-DIAMINE) with 4,4′-diphenylmethane diisocyanate (DMDI) and tolylene 2,4-diisocyanate, respectively. NLO copolyurea was prepared from DMDI with 2R-DIAMINE and m-phenylene diamine. TPU and TPU2 gave d33 values of 12.5 and 9.8 pm/V, respectively, under optimum poling conditions. A time-dependent decay curve of second-order nonlinear susceptibility was fitted well with a Kohlrausch–Williams–Watts stretched exponential function. The relaxation time of TPU2 was 4.2 × 108 s at 100 °C. Copolyurea was uniaxially drawn in ratios of 1.5 and 2.0. The average molecular angles ΦX, ΦY, and ΦZ in three laboratory frames were evaluated from the refractive indices. ΦY decreased and ΦX and ΦZ increased with an increasing draw ratio. The dependence of the second-order harmonic intensity on the incidence angle, that is, the Maker fringe pattern, was fitted with two independent tensor components, d33 and d31, for undrawn film and five independent tensor components, d33, d32, d31, d15, and d24, for drawn films. For drawn films, Kleinman symmetry was not satisfied: d31 ≠ d15 and d32 ≠ d24. An increase in the draw ratio gave rise to a large increase in the tensor component d33. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 247–255, 2001

Thermal stability and transmission losses of the poled polyimide side-chain thin films

The new side-chain polyimide thin films have been prepared. Through in situ second-harmonic generation (SHG) measurement, the corona poling temperature has been optimized by measuring the temperature dependence of in situ SHG signal intensity under the poling electric field. The second-order NLO coefficient χ 33 (2)=5.6 pm/V at λ=1064 nm was determined by using Maker fringe method after poling the films at optimal poling condition. The depoling knee temperature of the poled polyimide films can reach up to 200°C. Their lower-order optical waveguide-propagation losses were measured at 632.8 nm. The measurements have shown that the optical loss of the fundamental mode is less than 1.0 dB cm −1 for TE polarization.

Investigation on the nonlinear optical properties of the DCNP/PEK-c guest–host polymer films

The polyetherketone (PEK-c) guest-host polymer thin films doped with 3-(1,1-dicyanothenyl)-1-phenyl-4,5-dihydro-1H-pryazole (DCNP) were prepared. The polymer films were investigated with in situ second-harmonic generation (SHG) measurement. The corona poling temperature was optimized by the temperature dependence of the in situ SHG signal intensity under the poling electric field applying. The temporal and temperature stability of the second-order properties of the poled polymer film were measured by the in situ SHG signal intensity probing. The second-order NLO coefficient chi ((2))(33) = 32.65 pm/V at lambda = 1064 nm was determined by using the Makel fringe method after poling under the optimal poling condition. The dispersion of the NLO coefficient of the guest-host polymer system was determined by the measured value of chi ((2))(33) at 1064 nm and the two-level model.

Optical intensity modulator based on a novel electrooptic polymer incorporating high /spl mu//spl beta/ chromophore

We have synthesized a novel electrooptic (EO) polymer based on a high /spl mu//spl beta/ chromophore incorporating tricyanobutadiene acceptors. A crosslinked polyurethane network was also adopted to enhance its thermal stability. In order to find the optimum poling condition for the polymer, the influence of the electric poling profile on optical characteristics such as the EO effect, thermal stability, and damage was investigated. Then a high-speed intensity modulator using the EO polymer was designed and fabricated. The measured half-wave voltage V/sub /spl pi// was 4.5 V at the wavelength of 1.31 /spl mu/m. Accordingly, the achieved EO coefficient r/sub 33/ was as high as 25 pm/V, and the thermal stability of the poled polymer was as high as 95/spl deg/C. Finally, the modulator was successfully operated up to 40 GHz.

Poling and characterization of nonlinear polymer DCNP/PEK-c thin films

Polyetherketone (PEK-c) guest–host polymer thin films doped with 3-(1,1-dicyanothenyl)-1-phenyl-4, 5-dihydro-1H-pryazole (DCNP) were prepared. The poling profiles of the polymer film were investigated by using the in situ second-harmonic generation (SHG) measurement. The corona poling condition was optimized by the poling profiles. The second-order nonlinear optical (NLO) coefficient χ 33 (2)=20.86 pm/V at λ=1064 nm was determined by using the Maker fringe method after poling under the optimal poling condition. The temperature stability of the second-order optical properties of the poled polymer film was measured by the in situ SHG intensity probing. Moreover, the relaxation of the electric field-induced polar orientation of the chromophores in the poled polymer film was measured by the thermally stimulated discharge current (TSDC) technique.

Nonlinear optical (NLO) polymers. IV. Second-order optical nonlinearity of NLO polyurea and copolyurea with NLO dipole moments aligned transverse to the main backbone

This article presents the molecular orientation and second-order optical nonlinearity of newly prepared polyureas and copolyurea with dipole moments aligned transverse to the main backbone. Nonlinear optical (NLO) polyureas, TPU and TPU2, were prepared from 2,4-diamino-4'-nitroazobenzene (2R-DIAMINE) with 4,4'-diphenylmethane diisocyanate (DMDI) and tolylene 2,4-diisocyanate, respectively. NLO copolyurea was prepared from DMDI with 2R-DIAMINE and m-phenylene diamine. TPU and TPU2 gave d 33 values of 12.5 and 9.8 pm/V, respectively, under optimum poling conditions. A time-dependent decay curve of second-order nonlinear susceptibility was fitted well with a Kohlrausch-Williams-Watts stretched exponential function. The relaxation time of TPU2 was 4.2 × 10 8 s at 100 °C. Copolyurea was uniaxially drawn in ratios of 1.5 and 2.0. The average molecular angles Φ X , Φ Y , and Φ Z in three laboratory frames were evaluated from the refractive indices. Φ Y decreased and Φ X and Φ Z increased with an increasing draw ratio. The dependence of the second-order harmonic intensity on the incidence angle, that is, the Maker fringe pattern, was fitted with two independent tensor components, d 33 and d 31 , for undrawn film and five independent tensor components, d 33 , d 32 , d 31 , d 15 , and d 24 , for drawn films. For drawn films, Kleinman symmetry was not satisfied: d 31 ¬= d 15 and d 32 ¬= d 24 . An increase in the draw ratio gave rise to a large increase in the tensor component d 33 .

Dielectric Properties and Poling of Potassium Lithium Niobate Crystals

We report the dielectric properties of the crystals K3Li2—xNb5+xO15+2x with x varied from 0.05 to 0.3, which were grown by the edge-defined film-fed growth technique. The optimum poling conditions were experimentally determined. The resulting polarity was checked by using etching techniques and measurement of the pyroelectric coefficient.

Improved optical nonlinearity of poled stilbene doped polymer films

The optical properties of corona poled 4′-N,N-dimethylamino-nitrostilbene (DANS) and a newly synthesized α′-cyano-4′-nitro-4-N,N-dimethylaminostilbene (CNDS) doped poly(methyl methacrylate) (PMMA) film were investigated with in situ second-harmonic generation (SHG) measurement and absorption measurement. Optimum corona poling temperatures of these polymer films were found to be lower than glass transition temperatures of the materials, most probably due to the dramatic increased conductivity of the films and phase separation. Under the optimum corona poling condition, the alignment ordering of CNDS was lower than that of DANS from the absorbance before and after corona poling. But the second-order nonlinear susceptibility χ (2) of CNDS/PMMA is improved compared with that of DANS/PMMA. The molecular second-order polarizability β of the CNDS/PMMA was estimated to be about 140 × 10 −30 esu from the measured absorbance and χ (2). The relaxation of SHG intensity of CNDS/PMMA was slower than that of DANS/PMMA. This showed that CNDS is a kind of better dopant than DANS as second-order nonlinear-optical material.

Quantitative analysis of piezoelectricity in simultaneously stretched and corona poled polyvinyl chloride films

Piezoelectric activity in cyclohexane-treated polyvinyl chloride films has been found to increase when processed under simultaneously stretched and corona poled (SSCP) conditions. The piezoelectric coefficient d31=7.2±1.1 pC/N was obtained in these films under optimum poling conditions. The main contributor to the improved piezoelectricity has been the increased dipolar polarization. Crystallinity and compliance have contributed marginally to the former. Thermally stimulated current (TSC) experiments show that maximum oriented dipole density has been achieved during the SSCP. Dipolar polarization ≈10−2 C/m2 has been obtained. The TSC and the shrinkage effect involving molecular rotation and/or chain motion are closely related. An application of the extended Mopsik and Broadhurst theory shows that 56% of the measured d31 is due to the dimensional effect and 44% due to the local field effect.

Effect of poling process on the piezoelectric and dielectric properties of Nb and Sr-doped PZT ceramics

The piezoelectric and dielectric properties of Sr and Nb doped lead zirconate titante (PZT) used for electroacoustic transducers have been investigated as a function of the poling field and poling time. The optimum poling conditions were determined from the measurement of maxima of the radial planar coupling factor (kp) and the relative dielectric constant (εr) at various poling parameters. The data showed that the mentioned quantities reach the maximum values and then saturate at an external electric field up to the saturation field in a suitable time. Large external fields associated with the extension of poling time above the optimal values produced the degradation of investigated electromechanical coefficient and the dielectric constant.

Effect of poling conditions on second-harmonic generation in fused silica

A systematic study of the effects of poling time and applied voltage on second-harmonic (SH) generation in thermally poled silica glass reveals that the SH signal is proportional to the square of the applied voltage and that the speed of the poling process increases with the applied voltage. Prior treatment of the samples is found to affect the poling process, and the optimum poling conditions are observed to depend on the poling atmosphere. The mechanism of thermal poling is discussed in the light of these new results.

Enhanced second-harmonic response and stability of corona-poled guest?host polycarbonate thin films

Second-harmonic generation and spectroscopic absorption measurements were made to study the non-linear optical and stability properties of guest/host polycarbonate thin films in which the guest chromophores were oriented by corona poling. Optimum poling conditions were achieved at temperatures less than the glass-rubber transition temperatures. Stabilized order parameters as high as 0.23 and retention of orientational order as high as 86% were found. Stable, resonance-enhanced, values of the non-linear optical coefficient d33, for the fundamental of 1.064 Μm, were as high as 31 pm V−1. This value is over four times that predicted by a simple thermodynamic model for isotropic materials. Hydrogen bonding between the guest and polycarbonate is proposed to account for the high d33 coefficients and long-term stability of the films.

Second-order nonlinear optical properties of poled coumaromethacrylate copolymers

Second-order nonlinear optical properties of newly designed and synthesized coumaromethacrylate side-chain polymers are reported. The optimum poling conditions were determined experimentally. The optimum poling temperature for these side-chain polymers is well above the glass transition temperature. The second harmonic coefficient of films poled by coronaonset at elevated temperature and the linear electro-optic coefficient of films poled by contact electrodes were measured. The stabilized value of the second harmonic coefficient, d33, at 1064nm fundamental wavelength was found to be 13 pm/V. The linear electro-optic coefficient, r33, exhibits strong dispersion ranging from 2 to 12pm/V in the wavelength range 477 to 1115 nm.

0-3 composite sensitivity

Abstract The sensitivity of 0-3 composites based on a modified lead titanate has been investigated. The effects of poling field, poling time and poling temperature will be shown. Based on these variations, optimum poling conditions have been estimated. The problems associated with a resistivity imbalance have been addressed with reversible changes based on moisture content within the sample.