Electro-optic Kerr Effect Research Articles

New polyamides with main-chain cyanine chromophores

Polyamides containing main-chain cyanine chromophores are synthesized, and their molecular, nonlinear optical, and mechanical properties are studied. It is shown that the Kerr electro-optical effect in polymer solutions is determined by the rigidity of polymer chains and that the nonlinear optical properties are dependent only on the chromophore content.

P‐146: Chiral Pitch Dependence of Electro‐optic Kerr Effect in Polymer Stabilized Blue Phase

AbstractPolymer stabilized blue phase (PSBP) with different chiral pitch was prepared to investigate the relation between electro‐optic response and the chiral pitch of PSBP. The stabilized temperature ranges of each PSBP were around 100 K. The effect of the chiral pitch of PSBP on the Kerr constant and the response time was almost same with the result of pure blue phase (BP) that is the Kerr constant of PSBP was proportional to the cube of the chiral pitch.

Electro-optic Kerr effect in polymer-stabilized isotropic liquid crystals

The electro-optic Kerr effect with a high Kerr constant around 10−9 m/V2 was observed in the polymer-stabilized isotropic liquid crystals over a wide temperature range. Optical isotropy at the field-off state was attained with randomly oriented domains of (chiral) nematic liquid crystals formed by a polymer matrix cured in the isotropic phase. Optical birefringence in the field-on state was induced by the reorientation of liquid crystals in the domains. Rapid rising and falling response times of the cells around 0.26 ms (0.52 ms total response time) were achieved. A theoretical model was proposed to explain the experimental results and agreed well with the results.

電気光学効果とCT法を利用した電界分布測定法の精度向上手法

Computed tomography (CT) method has been used for industrial application as well as it has been mainly developed in a medical field. We have investigated the measurement of nonuniform electric field vector distributions in liquid dielectrics using an original method based on electrooptic Kerr effect and CT method. In applying CT method to the reconstruction of the electric field, a principle of CT method has been faithfully observed, which has been one of cause of the error. Specifically, region passing through of the light for measurements was not equal to the reconstructed region and the electric field was reconstructed without consideration of the value of cells outside of the region for reconstruction. So, to solve these problems, we suggested the improved algorithm for reconstruction using the concepts which we called “actual region projection data” and “extension of region for reconstruction”. By a simulation and an experiment, the usefulness of the improved method was studied.

Kerr and Faraday effects in borate glasses

Electrooptic Kerr and magnetooptic Faraday effects are studied in LiKB4O7, Li2B6O10 and LiCsB6O10 glasses. The corresponding quantitative coefficients are determined for the wavelength of 632.8 nm. It is shown that the above compounds can be used as electrooptic and magnetooptic materials which are highly resistant to powerful optical radiation and transparent in the ultraviolet spectral range.

Liquid crystalline amorphous blue phase and its large electrooptical Kerr effect

An amorphous blue phase III with low and wide thermal range (∼20 °C) including room temperature is induced by doping a bent-core nematic with a strong chiral material. We confirm that the electrooptical response is due to the Kerr effect, with the Kerr constant being up to two orders of magnitude larger than conventional Kerr materials such as nitrobenzene.

Electro-optical Kerr effect in the isotropic phase of the two antiferroelectric liquid crystal mixtures

We have experimentally studied for the first time the electro-optical Kerr effect and the pre-transitional behavior in the isotropic phase of two antiferroelectric liquid crystal mixtures, W-232 and W-204D, composed of rod-like ester molecules exhibiting the direct smectic-A to isotropic (SmA-I) phase transition. The Kerr law has been confirmed for the two compounds and the variation of inverse Kerr constant with temperature above the smectic–isotropic transition temperatures were determined. Both the mixtures with very broad antiferroelectric phase around room temperature have similar sequence of the phases (i.e., Cr-SmC*A-SmC*-SmA-I). Although, the pre-transitional behavior is usually complex in the isotropic phase of the chiral smectic liquid crystal compounds, the investigated compounds showed a similar behavior compared to that of nematic–isotropic behavior.

Photoluminescence and Electro-Optic Kerr Effect in Porphyrin Derivatives of C60

Photoluminescence and electro-optical properties of two C60 fullerene derivatives: with porphyrin (C60-H2P) and of an iodide salt of Zn porphyrin (C60-ZnP)+I− are reported. Both studies were done in solution. In the case of the (C60-H2P) the photoluminescence spectra depend strongly on the solvent used and emission from B band is quenched in dioxane. For the idodide salt [C60-ZnP]+I− both emissions from B and Q bands are observed. In all studied cases the photoluminescence at 650 nm is present, however it is excited in the iodide salt only for certain excitation energies. The EO Kerr effect measurements show a very slow rotation of molecules under the applied electric field. This rotation is more complex in the case of the iodide salt.

Optical measurement of electric field distributions with time in a liquid at DC pulse voltage

AbstractFor electrical insulation diagnosis, it is necessary to obtain information about the electric field distribution and the space charge distribution in insulation materials. We have investigated the measurement of nonuniform electric field vector distributions in liquid dielectrics using an original method based on the electrooptic Kerr effect and the CT method. We developed an optical system that could measure electric field distributions in about 1 ms. In this study, when a DC voltage pulse of 50 ms width was applied to a sphere‐to‐plane electrode system, electric field distributions on some measurement planes were measured at intervals of 1 ms. The distribution a short time after application of the voltage pulse seemed to be disturbed. It is inferred that the “disturbance” was caused by changes in the density of the liquid due to movement of certain carriers in the liquid. Observation of the time of onset of the disturbance would make it possible to determine the behavior and electric characteristics of the liquid. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 172(1): 1–9, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20940

Correlation between the electro-optical Kerr effect and physical parameters of nematogens

The relationship between the Kerr effect in an isotropic phase in the vicinity of phase transition temperature ( T NI) from isotropic to nematic phase and material parameters of the nematogens has been investigated. We could conclude that a strong correlation was confirmed between the Kerr constant in the vicinity of T NI and the material parameters; the larger Kerr effect was observed in the prepared nematogen that also had larger product value of Δ n × Δ ε × K 33/ K 11, which can be useful knowledge for designing novel nematogens with high Kerr constant.

Mesomorphic Poly(aryl ester)/Poly(benzyl ether) Dendrimers/co-Dendrimers with C60 as the Core

Structure-properties relations of liquid crystalline fullerene-containing poly(aryl ester)/poly(benzyl ether) dendritic compounds with variation of C60 linkage type have been analyzed based on experimental data on their total polarity and electro–optical Kerr effect in benzene solutions. There was established that fulleropyrrolidine as the core of dendrimer strongly restricts rotational freedom of dendrons, in contrast to methanofullerene. A conclusion that not only terminal mesogenic groups and dendrons' generation number, but a manner of C60 incorporation into the dendritic matrix also influences on the mesomorphic behavior of these multicomponent hybrid-type liquid crystalline compounds had been made.

Phase diagram and electro-optical Kerr effect of nematic mixtures containingtolane and biphenyl cores

An experimental phase diagram for two types of nematic liquid crystals and their binary mixtures was established by polarised optical microscopy and differential scanning calorimetry methods. The mixtures comprised a tolane-base liquid crystal, 4-heptyl-3-fluoro-4-isothiocyanatotolane (7TOLF), and a biphenyl-base nematogen, 4-heptyl-3-fluoro-4-isothiocyanatobiphenyl (7BF). The static Kerr effect and third-order non-linearity were investigated for 7TOLF and 7BF and their nematic mixtures within the isotropic phase. Both the compounds have a positive and large Kerr constant. The second-order phase-transition temperatures, T*, were determined for these mixtures. The linear dependence of (T - T*)− 1 on the Kerr constant is found to be in good agreement with the predications of the Landau–de Gennes model. The third-order non-linear susceptibility,χ(3), values were determined for these mixtures.

Optical study of prebreakdown cathode processes in deionized water

The initial stage of prebreakdown cathode processes is studied with the help of the shadow method and electrooptical Kerr effect with laser light exposure of ≈ 3 ns. Experiments are performed by using triangular voltage pulses with time rise of ≈ 1 μs, time decay of μ 0.1 μs and total width of < 2 μs. The distance between electrodes 50 mm in diameter is 3 - 5 mm. Field strength varies from 275 kV/cm up to 500 kV/cm. Initial separate optical heterogeneities of size of 50-100 μm are registered at E ≥ 380 kV/cm. Spherical density disturbances with epicenter placed over the cathode are registered when the cathode "bush" reaches the size of ≥ 100 μm. In front of the "bush" the enhancement of electric field exceeding the average field several times in the gap is registered. However, fast discharge is developed from anode. Experiments performed without restriction of voltage pulse duration at E ≈ 300 kV/cm show that within 6 - 8 μs cathode disturbances increase up to the size of 2 - 4 mm and initiate the breakdown. The EHD model of subsonic cathode streamer development is considered.

プロピレンカーボネート中の電界分布の光学的時系列測定

Electrical insulation diagnosis requires that we obtain information about the electric field distribution and the space charge distribution in insulating materials. We have measured nonuniform electric field vector distributions in liquid dielectrics by our original method based on the electrooptic Kerr effect and the CT method. We carried out time sequence measurement of the electric field vector distribution in propylene carbonate, which is a dielectric liquid. When a DC voltage pulse of 200-ms width was applied to a parallel plane electrode system, the electric field vector distributions, which had the shape of a circle 12 mm in diameter, were measured at time intervals of 3 ms. The measurements were carried out while varying the conductivity of the liquid. The distribution a certain time after applying the voltage pulse seemed to be disturbed. Observation of the time at which the disturbance started would make it possible to determine the behavior and electrical characteristics of the liquid. We also studied the evaluation of remnant charges. © 2011 Wiley Periodicals, Inc. Electron Comm Jpn, 94(9): 45–51, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10351

Proposal for electro-optic multiplier based on dual transverse electro-optic Kerr effect

A novel electro-optic multiplier is proposed, which can perform voltage multiplication operation by use of the Kerr medium exhibiting dual transverse electro-optic Kerr effect. In this kind of Kerr medium, electro-optic phase retardation is proportional to the square of its applied electric field, and orientations of the field-induced birefringent axes are only related to the direction of the field. Based on this effect, we can design an electro-optic multiplier by selecting the crystals of 6/mmm, 432, and m3m classes and isotropic Kerr media such as glass. Simple calculation demonstrates that a kind of glass-ceramic material with a large Kerr constant can be used for the design of the proposed electro-optic multiplier.

Quadratic Electro-Optic Kerr Effect: Applications to Photonic Devices

We propose novel applications of the quadratic electro-optic Kerr effect to photonic devices. Specifically in this work, two new illustrative examples are described, namely an electrically controlled multistable switch (ECMS), and an electrically tunable Bragg grating (ETBG). Their functionality is based on the third-order nonlinearity in an isotropic medium. On one hand, we note that the first key feature is the all-optical as well as electro-optical control/tunability. This can be achieved only in the third-order nonlinear material as opposed to a more frequently used linear electro-optic effect exploited in optical crystals. On the other hand, the second important key feature is the availability of integrated and compatible materials that show third order nonlinearity. In the first application proposed here, ECMS, the interplay between the quadratic electro-optic and all-optical Kerr effects is crucial for its tunable operation and leads to an interesting feature of storing an electrical information optically. In the second example, ETBG, employing the quadratic electro-optic effect makes it attractive thanks to the existence of the third-order nonlinearity in many interesting isotropic materials that are suitable for device integration. Devices such as modulators, switches, mixers, variable attenuators or optical limiters can be designed.

Space-charge-controlled electro-optic effect: Optical beam deflection by electro-optic effect and space-charge-controlled electrical conduction

This paper describes the experimental and theoretical studies of an anomalous optical beam deflection phenomenon based on electrooptic effect and space-charge-controlled electrical conduction. In the experiment, a large deflection angle of 250mrad (=14.3°) has been observed by applying ±250V to a 0.5-mm-thick KTa1−xNbxO3 crystal with a short interaction length of 5.0mm. The crystal has a rectangular shape with uniform electrodes and there is no prism shape involved which is a common geometrical shape of crystal, electrode, or ferroelectric domain in the conventional electro-optic deflectors. The operating principle is investigated and it is found that the space-charge-controlled electrical conduction in the crystal plays an essential role in this deflection phenomenon. The electrical conduction is carried by electrons injected from the Ohmic contact of the electrode with the crystal. The injected electrons induce the space-charge effect and the electric field becomes nonuniform between the electrodes. The theoretical analysis shows that the electric field has a square-root dependence on the distance from the cathode. As a result, a linearly graded refractive index is induced by the electrooptic Kerr effect of the crystal and the optical beam is cumulatively deflected as it propagates in the crystal. We named this effect the “space-charge-controlled electro-optic effect” and the factors related to the onset of this effect are also discussed.

Electronic control of soliton power transfer in silicon nanocrystal waveguides

We demonstrate numerically that the power transfer from one polarization component of a (1+ 1)D vector spatial soliton to the other in a birefringent nonlinear medium can be controlled via the electro-optic Kerr effect by varying the externally applied electric field. We show how several all-optical operations involving fundamental vector solitons can be electronically controlled. We also discover that the split-up of the higher-order vector solitons due to the two-photon absorption (TPA) can be suppressed by adjusting the external electric field. The soliton trapping along the slow optical axis is realized by a planar waveguide, filled with a silicon-nanocrystal material. The external electric field is applied along the fast optical axis of the waveguide.

Coupled Simulation of Tunable Microoptic Devices

An approach for the implementation of unidirectional multiphysics resulting in a change of the refractive index in high-frequency applications is provided. The method addresses material effects like thermooptic effect, Pockels and Kerr electrooptic effect, photoelastic effect, thermal expansion and converse piezoelectric effect for modulation of optical circuits in wave propagation software. As an example, the wave propagation in a Fabry-Perot interferometer subjected to mechanical strain is considered.

Interference and electro-optical Kerr effects responsible for electroabsorption spectra of transparent Parylene-C films

Electroabsorption spectra of Parylene-C films are found to exhibit several peaks whose wavelengths depend on the thickness of the film. The spectral feature is well correlated to the first derivative of the transmission spectrum of the Parylene-C film sandwiched between two reflective metal layers, and the peak intensities are in proportion to the square of the magnitude of a modulation voltage. The electroabsorption spectra observed in a transparent region of the electrically insulating films are accounted for in terms of the interference effect coupled with the electro-optical Kerr effect of the Parylene-C films.