Showing papers on "Kerr effect published in 1972"

Kerr Effect in the Isotropic Phase of Some Nematogenic Compounds

Abstract: The exceptionally strong Kerr effect of some nematogenic compounds with strong electric dipole moments parallel to their long molecular axes was investigated. The Kerr constants just above the clearing point T cl were about 100 times larger than with nitrobenzene. The temperature dependence of the Kerr effect obeyed (T-T cl)−y, with 0.5<γ<0.7. The relaxation times were 4.10−7 sec or less.

Structure of Dielectric Fluids. II. The Free Energy and the Kerr Effect in Polar Fluids

Abstract: The Helmholtz free energy of a molecular fluid of rigid dipoles in the absence of any external field is studied. An explicit formal expression for the excess free energy due to the dipolar interaction is found. It is shown that the free energy per particle is independent of the shape of the sample, although shape‐dependent long‐range correlations are present in the fluid. For the special case of the Onsager model of polar fluids an explicit expression is obtained for the contribution to the free energy due to the dipolar interactions. Next, we study the long‐range part of the three‐particle correlation function for an arbitrarily shaped sample of the molecular fluid in the absence of an external field. This long‐range part is dependent on the shape of the sample. The three‐particle correlation function arises in the expression for the Kerr constant, which measures the birefringence of the fluid when a strong electric field is applied. We show explicitly that, in the lowest nonvanishing order in the field, the birefringence is proportional to the square of the resulting local macroscopic electric field with a proportionality constant (the Kerr constant) which is independent of the shape of the sample. A formal expression is given for the Kerr constant in terms of the local properties of the fluid.

Nematogenic material which exhibit the kerr effect at isotropic temperatures

Abstract: WHEREIN R is n-butyl, n-pentyl, n-hexyl, N-HEPTYL OR N-OCTYL, OR MIXTURES THEREOF OR MIXTURES OF THESE COMPOUNDS WITH OTHER NEMATOGENIC SUBSTANCES. WHEREIN R is ethyl, n-propyl, n-butyl, n-pentyl, N-HEXYL, ISOHEXYL, N-HEPTYL OR N-OCTYL OR COMPOUNDS OF THE GENERAL FORMULA An electro-optical light-modulation cell having a dielectric disposed between electrodes and being comprised of a nematogenic fluid in the isotropic state, is described. Said dielectric, upon application of a voltage to the electrodes, becomes double refracting. More particularly the nematogenic fluid comprises compounds of the general formula

Rotatory Motion of Dipolar Molecules Constrained by a Steady Electric Field

Abstract: In this paper a calculation has been carried out on the rotatory diffusion of dipolar rodlike molecules in the presence of an electric field. The time correlation method is used for calculations of dynamic susceptibilities. This calculation has been shown to be in good agreement with the dynamic dielectric studies of Block and Hayes. In addition, the decay of electric birefringence (Kerr effect) in the presence of an electric field has been shown to be extremely sensitive to the relative magnitudes of the steady state field and the initially applied sensing field.

Electro-optical light-modulation cell utilizing a nematogenic material which exhibits the kerr effect at isotropic temperatures

Abstract: An electro-optical light-modulation cell having a dielectric disposed between electrodes and being comprised of a nematogenic fluid in the isotropic state, is described. Said dielectric, upon application of a voltage to the electrodes, becomes doubly refracting.

Direct observation of the orientational Kerr effect in the self-focusing of picosecond pulses.

Abstract: Direct measurements of the relaxation time of the birefringence within the self-focusing region of mode-locked laser pulses in several anisotropic liquids establish the importance of the orientational Kerr effect in the picosecond time regime. This result leads to some speculation as to the origin of the high degree of symmetry in the phase-modulated filament spectra observed with picosecond pulses.

Pulsed Laser Kerr System Polarimeter for Electro‐Optical Fringe Pattern Measurement of Transient Electrical Parameters

Abstract: Novel electro‐optical fringe pattern methods are developed for measurement of transient high voltages and electric fields. Several techniques employing the Kerr effect, a pulsed laser source, and high speed photographic recording equipment are described. Typical fringe pattern results are compared with conventional resistive divider measurements.

Measurement of 60 Hz voltages using the Kerr effect

Abstract: The Kerr effect has been used to measure 60 Hz alternating voltage up to 30 kV peak. The system behaves much as it does under the influence of a short high‐voltage pulse except that in this case the frequency of the applied voltage is sufficiently low that the space charge effects in the liquid are not negligible.

Faraday and Kerr Effects of Hot Electrons in n‐Type InSb in the Infrared (I)

Abstract: The nonparabolicity of the conduction band and the anisotropy of the hot electron distribution function have been shown to lead to the anisotropy of the refraction index in strong electric fields (Kerr effect). Nonparabolicity causes also a decrease of the Faraday rotation angle θ when the electron gas is heated. A comparison of the calculated values of Δθ with the experimental ones allows to determine the temperature of hot electrons for n-type InSb with concentrations of the electrons in the range of 3 × 1014 to 4.9 × 1015 cm−3 at T0 = 80 °K in longitudinal magnetic fields. The interaction constant with polar optical phonons was also determined. The influence of e-e collisions on the distribution function of hot electrons is discussed. [Russia Text Ignore].

Dynamic detection of faraday rotation

Abstract: A wide bandwidth scheme for the detection of the Faraday and Kerr effects is presented. An electrooptic modulator is utilized to give an output signal in the form of a 100% amplitude modulated carrier, and provides laser and surface noise rejection capability in a single-ended arrangement. The system configuration is such that problems of temperature sensitivity and drift associated with EO modulators have minimal effect on the overall performance.

Relative importance of electrostriction and the Kerr effect to self-focusing in optical glasses

Abstract: The damage threshold for three optical glasses was found to be higher for circularly polarized radiation than for linear polarization, using 26‐nsec pulses from a Nd:glass laser. The damage was assumed to result from self‐focusing. The fractional contribution of electrostriction to the total nonlinear index n2 is estimated to be 0.8 ± 0.2 for borosilicate crown glass, 1.15 ± 0.35 for fused silica, and 0.4 ± 0.1 for dense flint glass, assuming the Kerr effect to be the only other self‐focusing mechanism. The data are consistent with present concepts of glass structure. The high damage threshold in fused silica is attributed to its relatively small Kerr effect.

Kerr Effect in Atoms and Molecules

Abstract: A time‐dependent double perturbation—variation formulation for the hyperpolarizabilities involved in the Kerr effect is presented which is suitable for quantitative study of the Kerr effect. It is applied to the hydrogen atom to generate accurate Kerr dispersion curves for a wide range of wavelengths, including the first two lines of the Lyman series. In the vicinity of resonance frequencies, the dominant term [(νi 2 − ν2)−3] approximation is shown to be good for quite a wide range of wavelengths.

A signal processing technique to obtain Kerr-effect M-H loops

Abstract: A technique is outlined whereby the surface M-H relationship on manganese-zinc ferrite single crystals may be obtained using a signal averager to improve signal-to- noise ratio. Unwanted magnetostrictive components are removed by computer-aided Fourier analysis. The method is used to obtain a surface M-H loop using the longitudinal Kerr effect to detect the fluctuation in surface magnetization.

Hot Electron Kerr Effect in Semiconductors with Non‐Parabolic Dispersion Law of Energy

Abstract: The phenomena of birefringence and plasma frequency splitting in semiconductors with isotropic non-parabolic dispersion law of carrier energy in the presence of a dc electric field have been considered on the basis of expressions obtained in a previous work [l]. n-InSb is taken as an example for the numerical calculations. It is shown that the phase shift due to the birefringence can attain a considerable value. The effect can, in principle, be used for creation of modulators, shutters, and circulators of electromagnetic radiation in the infrared range. [Russian Text Ignored.].

The free carrier magneto-microwave Kerr effect in p type germanium at 296 K and 77 K

Abstract: The reflection of microwave radiation from the surface of a p type germanium sample placed in a static magnetic field in the direction of propagation has been studied in terms of Rg, the amplitude ratio of the two orthogonal linearly polarized components of the reflected wave. The experimental analysis applies to guided waves and treats multiple reflections exactly. A good agreement between theory and experiment has been found at both 296K and 77K. In the theoretical calculation, the contributions from light and heavy holes are considered separately. The value of the relaxation time for light holes has been found to be 0.81*10-12s, which is fairly close to the value of 0.96*10-12s which has been obtained by Baynham (1968) when ionized impurity scattering is included in the theoretical estimation of the relaxation time. The value of the relaxation time estimated for a heavy hole is 4.3*10-12s, which agrees with the values estimated by earlier workers.

Investigation of self-focusing in the case of stimulated Raman scattering of light

Abstract: An investigation was made of the influence of different excitation conditions on the self-focusing of stimulated Raman-scattered light It was found that the dimensions of self-focusing filaments and their number depended on the energy of the exciting radiation and the thickness of the scattering layer In the situation in which self-focusing points were observed at both ends of a Dewar flask, the anti-Stokes scattering included (in addition to rings of class 1) scattering along the axis Estimates were obtained of the self-focusing threshold power related to the Kerr effect and to the increase in the polarizability of molecules due to excitation It was found that the first of these mechanisms could not give rise to self-focusing of the Raman-scattered light, whereas the threshold of the second mechanism was close to the excitation energy at which such self-focusing was observed

Dipole moments, molar kerr constants, and three-dimensional structure of some 4,5-dihydro-1, 3,5-dithiazines

Abstract: The three-dimensional structure of some 4,5-dihydro-1,3,5-dithiazine derivatives was investigated by means of dipole moments and the Kerr effect. The presence of equilibrium boat and chair forms in the conformational mixture is proposed for the 2,4,6-trimethyl and 2,4,-5, 6-tetramethyl derivatives. Energy data that confirm the possibility of anomalous conformations are presented.

Optical Kerr effect in glass waveguide

Abstract: We have observed light induced birefringence in glass optical waveguide. This effect can be observed at low powers in waveguide because of the high power densities which are maintained over long lengths of guide. This effect is potentially useful as a wide‐band pulse modulator or as a device for switching or measuring the length of picosecond pulses.

On the maximization of the transverse Kerr magnetooptic effect

Abstract: Using perturbation theory, the transverse Kerr effect is analyzed for a magnetic substrate covered by one dielectric layer. It is shown that when the dielectric layer forms a nonreflecting coating of the substrate, both the change in the reflected light as well as the contrast are maximized.