Optical Kerr Constant Research Articles

Optical Kerr effect induced by picosecond light pulses in tRNA solutions

The optical Kerr effect (OKE) of tRNA solutions induced by picosecond light pulses of a YAG-Nd 3+ laser, λ = 1060 nm, was investigated. A weak He-Ne laser light beam, λ = 632.8 nm, served as the measuring beam. The experimentally determined molecular Kerr constants B mol NL, and previously obtained values of the molecular total Kerr constants B mol TOT, allowed for the calculation of the molecular orientational-redistributional components B mol OR+RE of the OKE constants. The mean third-order optical polarizabilities c ai were also determined. The B mol NL, B mol OR + RE and c ai parameters estimated for tRNA macromolecules in water and in two different buffer solutions with and without magnesium ions are discussed in the light of data obtained by other methods. For different tRNA structures, different values of the optical Kerr constants and third-order optical polarizabilities were observed. It was found that the linear optical parameters, i.e., optical polarizability a and anisotropy δ a , obtained in the present studies, are much smaller in comparison with corresponding values obtained from the static light-scattering measurements. The relative nonlinear optical Kerr constants in pure water and salt buffers were measured, and are found to be opposite in sign. The relative values of the optical Kerr constants of both buffer solvents obtained in our picosecond measurements are smaller by a factor of two than those obtained in nanosecond studies.

Anomalous behavior of the optical Kerr constant of nematogens far above the nematic-isotropic transition

Using Lin's Microscopic theory for the isotropic-nematic transition, we propose a new explanation for earlier experimental results where deviations of the optical Kerr constant of nematogens from the mean-field behavior were observed several degrees above the transition.

Optical Kerr effect in the isotropic phase of various alkyl-cyanobiphenyl homologues

Measurements have been made of the optical Kerr effect on four homologous members of the alkyl-cyanobiphenyl series of liquid crystals at temperatures above the nematic-to-isotropic clearing temperatures. Amplitudes of the birefringence and rotational relaxation times (τ) have been recorded as the temperature was increased from just above the clearing temperature for each system. From the data it was found that the optical Kerr constant B 0 had a temperature dependence of (T - T*)-1, similar to that predicted by the Landau-de Gennes equation. This persisted only for a very limited temperature range of a few degrees Celsius. Beyond this range, and for all samples, the existence of an additional temperature independent contribution to B 0 was evidenced.

Additional contribution, with no critical thermal behavior, to the optical Kerr constant of nematogens in their isotropic phases

Additional contribution, with no critical thermal behavior, to the optical Kerr constant of nematogens in their isotropic phases

Electronic and orientational contributions to the optical Kerr constant determined by coherent Raman techniques

We have used the Raman-induced Kerr effect to normalize the optical Kerr constants of several liquids to their corresponding Raman matrix elements. The electronic contribution to the Kerr constant was similarly normalized using three-wave mixing.

Optical-field-induced refractive indices and orientational relaxation times in a homologous series of isotropic nematic substances

We have measured the optical Kerr constant and the orientational relaxation times of seven $p$,${p}^{\ensuremath{'}}\ensuremath{-}\mathrm{di}\ensuremath{-}n\ensuremath{-}\mathrm{alkoxyazoxybenzene}$ homologous compounds as functions of temperature in the isotropic phase. The observed critical behaviors near the isotropic-nematic transitions agree well with the predictions from the Landau-de Gennes model. Various characteristic parameters of the homologs are deduced from the experiment. Their variations with increase of methylene groups in the alkyl chain are discussed. Our results suggest that neither the mean-field theory of Maier and Saupe nor the Landau expansion of free energy is a good approximation for quantitative description at the isotropic-nematic transition.

Laser-induced birefringence in polar liquids*

The high-frequency Kerr constants are measured for the first time for a variety of polar liquids relative to nitrobenzene, a strong Kerr-active liquid. Among the liquids investigated were aromatic compounds, ketones, and fluoroalcohols. The measurements consisted in inducing optical birefringence in the liquid samples by the intense electric fields from a Q-switched Nd:glass laser and simultaneously observing a pulsed signal through crossed polarizers using a low-power He–Ne laser as a light probe at 6328 Å. Comparison of the measured and calculated optical Kerr constants for those liquids where the depolarization ratios and isothermal compressibilities were known showed satisfactory agreement. A number of liquids exhibited high-frequency Kerr constants on the order of nitrobenzene.

Static and optical Kerr effect in the nematogen M.B.B.A.

The Kerr effect has been studied in the nematic liquid crystal M.B.B.A. both for its isotropic phase and in solutions in CCl4. Electric and high frequency laser fields were used and both Static and Optical Kerr constants evaluated. The laser-induced birefringence has been studied as a function of temperature, time and equivalent field strength. A sign reversal of the Kerr effect between direct current and optical frequency fields is reported both for the pure isotropic phase and for the material in solution. In addition the static field studies indicated that a sign reversal in d.c. fields might be obtainable as a function of solution concentration. The studies in the isotropic phase, when conducted over a limited temperature range, indicated that the short-range-order theory proposed by de Gennes is appropriate to this system.

Laser-induced birefringence in pure liquids

Abstract The optical Kerr effect has been studied in the six liquids carbon disulphide, pyridine, benzene, toluene, benzoyl chloride and nitrobenzene. By quantifying the equivalent laser field strength, the optical Kerr constants of these materials have been determined. The results obtained are in agreement with published depolarized Rayleigh scattering measurements. These experimental data have been applied in an appraisal of a number of published theories of the optical Kerr effect, all of which showed at best only order-of-magnitude agreement.

Intramolecular interactions. XXV. Internal rotation barriers of benzylic compounds. Molecular optical anisotropies, dipole moments, and Kerr constants

Intramolecular interactions. XXV. Internal rotation barriers of benzylic compounds. Molecular optical anisotropies, dipole moments, and Kerr constants

Intramolecular interactions. XXIV. Conformations of benzylic compounds. Molecular optical anisotropies, dipole moments, and Kerr constants

Intramolecular interactions. XXIV. Conformations of benzylic compounds. Molecular optical anisotropies, dipole moments, and Kerr constants

Transient stimulated Raman scattering in binary mixed liquids

Stimulated Raman scattering (SRS) spectra in several mixed liquids with a large optical Kerr constant are studied with nanosecond and picosecond light pulses. These spectra show a dependence of the SRS intensity on the relaxation times T 2 of Raman active modes.

Effet Kerr ultra-hertzien du sulfure de carbone

We will show that it is possible to detect and measure the Kerr effect in a microwave spectrum. We have verified Kerr's law and measured Kerr's constant at a frequency of 9227.12 MHz. We have shown that this value is compatible with the optical Kerr constant.

Optical Kerr constant measurement in some liquids and glasses

We have measured the optical Kerr constant of two glasses and two liquids, namely phosphoryl chloride and toluene. We find that the nonlinear indices n <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> are of same order of magnitude in glass and phosphoryl chloride.

Self-Modulation, Self-Steepening, and Spectral Development of Light in Small-Scale Trapped Filaments

The spectral broadening associated with light propagating in self-trapped filaments through liquids with large optical Kerr constants is studied. In particular, we treat the influence of a nonzero orientational relaxation time and of linear dispersion upon the phase (and amplitude) development of the light as it interacts with the optically nonlinear medium. Relaxation introduces Stokes-anti-Stokes asymmetry, even in the absence of pulse steepening. The spectrum is compressed, and the degree of interference in various portions of the spectrum is altered. The effect of dispersion is apparently much less important, particularly in the case where propagation distances are short compared with the shock distance. However, dispersion combined with a finite relaxation time does introduce an exponential gain in the forward direction. For a small nonlinearity, the peak gain is equal to the stimulated Rayleigh gain in the backward direction; but it falls off with increasing nonlinearity, because of the Stokes-anti-Stokes interaction.Spectra computed for a picosecond pulse and for a 100% sinusoidally modulated light beam of infinite extent are compared. Because of its periodicity, the latter possesses a fine structure and is influenced differently by the orientational relaxation.Comparison of the experimental results with the theoretical calculations for the cases of a zero and a nonzero relaxation time indicates that pulses of the order of 5-10 psec in extent could give rise to the observed spectra. Possible sources of such pulses (or a sequence of such pulses) are discussed.

Temperature effect on self-focusing of laser beam in liquids

Summary form only, as given. The interaction of light with acoustic excitations and molecular orientational excitations in liquids, a generalization of electrostrictive and optical Kerr effects, can lead to self-focusing of a laser beam. This gives rise to inhomogeneity or formation of hot filaments in the beam, and consequently, to many anomalous effects in the stimulated Raman scattering. The effect can be seen indirectly by the reduction in the Raman threshold of a Ramanactive medium with the insertion of a liquid cell in front of it. Experimental results show that the self-focusing effect occurs in both Raman-active and Raman inactive media, but is much stronger in liquids with large optical Kerr constants. Turbulence in the liquid cell also helps the self-focusing effect appreciably. It is therefore believed that the self-focusing of the beam is initiated by small-scale fluctuations in the refractive index of the liquid and in the laser intensity, and perpetuated through either the electrostrictive, or the optical Kerr effect, or both.

Electrostriction, optical Kerr effect and self-focusing of laser beams

Electrostrictive coefficients and optical Kerr constants for liquids are derived. Their relative importance in the self-focusing of a giant-pulse laser beam is discussed.