Electrooptic Kerr effect

Le KV, Aya S, Sasaki Y, Choi H, Araoka F, Ema K, Mieczkowski J, Jakli A, Ishikawa K, Takezoe H (2011) Liquid crystalline amorphous blue phase and its large electrooptical Kerr effect. J Mater Chem 21 2855-2857... 

A combination of molecular mechanics calculations and electric birefringence (electrooptical Kerr effect) measurements of group IVB aryl compounds has been used to study conformational effects in these molecules [504l... 

The photoinduced phenomenon where the change in refractive index is proportional to the second order term of applied voltage is called an electrooptical Kerr effect. Kerr cells of liquid or solid transparent media can be used together with polarizers to transmit or block light, depending on whether an electric field is applied or not. Such light switches have many uses in laser technology. 

O. Prezhdo, K. Olan, W. Zubkowa and W. Prezdo, Electrooptical Kerr Effect in Chemistry , Wiadomosci Chemiczne, 2011, 65, 1. 

Combination with Static Fieids. A common technique, useful for optoelectronic devices, is to combine a monochromatic optical field with a DC or quasistatic field. This combination can lead to refractive index and absorption changes (linear or quadratic electrooptic effects and electroabsorption), or to electric-field induced second-harmonic generation (EFISH or DC-SHG, 2 > = > - - third-order process. In EFISH, the DC field orients the molecular dipole moments to enable or enhance the second-harmonic response of the material to the applied laser frequency. The combination of a DC field component with a single optical field is referred to as the linear electrooptic (Pockels) effect co = co + 0), or the quadratic electrooptic (Kerr) effect ( > = > - - 0 -I- 0). These electrooptic effects are discussed extensively in the article Electrooptical Applications (qv). EFISH is... 

Experimental and theoretical results are presented for four nonlinear electrooptic and dielectric effects, as they pertain to flexible polymers. They are the Kerr effect, electric field induced light scattering, dielectric saturation and electric field induced second harmonic generation. We show the relationship between the dipole moment, polarizability, hyperpolarizability, the conformation of the polymer and these electrooptic and dielectric effects. We find that these effects are very sensitive to the details of polymer structure such as the rotational isomeric states, tacticity, and in the case of a copolymer, the comonomer composition. 

We have shown in this paper the relationships between the fundamental electrical parameters, such as the dipole moment, polarizability and hyperpolarizability, and the conformations of flexible polymers which are manifested in a number of their electrooptic and dielectric properties. These include the Kerr effect, dielectric polarization and saturation, electric field induced light scattering and second harmonic generation. Our experimental and theoretical studies of the Kerr effect show that it is very useful for the characterization of polymer microstructure. Our theoretical studies of the NLDE, EFLS and EFSHG also show that these effects are potentially useful, but there are very few experimental results reported in the literature with which to test the calculations. More experimental studies are needed to further our understanding of the nonlinear electrooptic and dielectric properties of flexible polymers. 

Solution characterization of poly(phosphazenes) is an important area of concern. Some of these studies were mentioned above in conjunction with the polymer synthesis. Electrooptical properties (Kerr effect) of PTFE have been examined. The Kerr constant was significantly higher than those of flexible chain polymers which was suggested to result... 

X < >o, cofc,-cofc) AC electrooptic effect, AC Kerr effect, Brillouin scattering, Raman scattering. Two-photon absorption High-speed optical gates... 

Kerr effect - An electrooptical effect in which birefringence is induced in a liquid or gas when a strong electric field is applied perpendicular to the direction of an incident light beam. The Kerr constant k is given by = k F , where X is the wavelength, E is the electric field strength, and and are the indices of refraction of the ordinary and extraordinary rays, respectively. 

P( P(-o> w,0) P(0 -fa>,w) Y( - Y(-2(i) (i>,tD,0) Y(-o) (i>,0,0) Second harmonic generation (SHG) Electrooptic Pockels effect Optical rectification Third harmonic generation DC electric-field-induced SHG Intensity-dependent refractive index Optical Kerr effect Coherent anti-Stokes Raman pSHG pEOPE pOR. yTHG. EFISH oj DC-SHG. JlDRI or. yOKE. yCARS... 

In electric-field-induced birefringence (or electrical birefringence, quadratic electrooptic effect, Kerr effect), an isotropic transparent substance becomes birefringent when placed in an electric field . The sample assumes the characteristics of a uniaxial crystal, the optical axis of which is parallel to the direction of the applied field. When the sample is illuminated normal to , the resulting two indices, and wj (which can be thought of as He and ), are associated with the parallel and perpendicular orientations, respectively. 

In Equation (14.7), the linear term vanishes and only the Kerr effect term survives. The electrooptic tensor for the Kerr effect varies with different molecular stmcture. For an isotropic Uquid, its quadratic electro-optic effect coefficients can be represented by the following matrix ... 

Optical Kerr Effect. Another important method used to characterize polymers is the optical Kerr effect (OKE). The optical Kerr effect differs from the quadratic electrooptic effect in that the birefringence effects are induced solely by an optical field (37). In this measurement, an intense linearly polarized pump pulse induces birefringence in the nonlinear sample through an intensity-dependent refractive index change. The sample is placed between crossed polarizers and a weak, typically tunable, continuous wave (cw) probe laser (usually at a different wavelength and polarized at 45° to the pump pulse) overlaps the pumped region. The increased transmission of the probe beam when the pump pulse arrives is proportional to (Xeff), a combination of elements of the tensor. Many... 

Because of the extensive overlap with electro-optics and nonlinear optics, the reader is referred to separate articles on these topics in this encyclopedia. See ElectroopticAL Applications for a discussion of the changes in the optical response of polymers dne to an applied AC or DC electric field from the so-called Pockels or Kerr effects. Also see, for an overview. Nonlinear Optical Properties. 

The first observation of natural optical anisotropy was made in 1669 by Bartolinius in calcite crystals, in which light travels at different velocities depending on the direction of propagation relative to the crystal structure. The electrooptic effect, electric-field-induced anisotropy, was first observed in glass in 1875 by J. Kerr. Kerr found a nonlinear dependence of refractive index on applied electric field. The term Kerr effect is used to describe the quadratic electrooptic effect observed in isotropic materials. The linear electrooptic effect was first observed in quartz crystals in 1883 by W. Rontgen and A. Kundt. Pockels broadened the analysis of this relationship in quartz and other crystals, which led to the term Pockels effect to describe linear behavior. In the 1960s several developments... 

Electrooptical properties and birefringence in an electric field (EBP). The Kerr effect—the birefringence induced in an electric field (EBF)— is another physical method of primary importance in the analysis of the properties of mesogenic polymas. 

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