Showing papers on "Kerr effect published in 1983"

PtMnSb, a material with very high magneto‐optical Kerr effect

Abstract: Results are reported of polar magneto‐optical Kerr effect measurements performed at room temperature on the Heusler alloy PtMnSb in the wavelength range 280–2000 nm. The double Kerr rotation has a maximum in excess of 2.5° at 720 nm, which is to our knowledge the highest room‐temperature Kerr rotation reported thus far for any material in the wavelength range under consideration. In order to assess the influence of composition the related materials PdMnSb, NiMnSb, and PtMnSn were also investigated. Here the Kerr effect was considerably lower.

Kerr electro‐optic field mapping measurements in water using parallel cylindrical electrodes

Abstract: An extensive set of Kerr electro‐optic field mapping measurements are reported for highly purified water over the temperature range of 8.8–29.5 °C. The Kerr constant is independent of temperature over this range and equals B≂3.4×10−14 m/V2. Pulsed high voltages up to 140 kV across parallel cylindrical electrodes with a 1‐cm gap are applied on millisecond time scales. For early times, the measured results agree with the space‐charge‐free electric field distribution while for times greater than 500 μsec, there is significant space‐charge distortion due to positive charge injection.

Photomagnetic recording medium

Abstract: PURPOSE:To improve the S/N ratio of a reproduced signal by laminating the 1st and the 2nd magnetic film layer which differ in refractive index on a transparent substrate and utilizing Fraday effect and Kerr effect in combination. CONSTITUTION:On the transparent substrate 5, the 1st magnetic layer 1 and the 2nd magnetic layer 2 are laminated. Both magnetic layers consists of vertically magnetized films which differ in refractive index sufficiently and reproducing light is reflected by the interface between the magnetic layers 1 and 2. The repoducing light A entered from the substrate side 5 is reflected partially by the surface of the 1st magnetic layer 1 and its reflected light B has the plane of polarization rotated by Kerr effect. The transmitted light has the plane of polarization rotated by Faraday effect, and also has the plane of polarization rotated by Kerr effect when reflected by the interface with the magnetic film 2 and the plane of the polarization rotated again by Faraday effect when transmitted through the magnetic film 1 to obtain reflected light C. The directions of rotations bt Faraday effect and Kerr effect are made coincide with each other. Consequently, the reflected light B and reflected light C become to be arithmetically, thereby improving the S/N ratio of reproduction.

Electro-Optic Measurement of the Electric Field Distribution in Transformer Oil

Abstract: A system has been developed to measure the electric fields in transformer oil using the electro-optic Kerr effect. The system performance was verified by measuring the electric field and space charge in nitrobenzene. The field distributions were measured in clean oil, in oil which had been used as a wash for a radiator used in a power transformer, and in oil which was removed from a transformer that had failed. Measurements were made from room temperature to 100°C. Under the conditions studied, the electric field strengths were generally within 10% of the strengths that would be predicted assuming that space charge was negligible.

Coherent phenomena involved in the time-resolved optical Kerr effect

Abstract: The effect of parametric coupling between pump and probe beams in time-resolved optical Kerr effect is theoretically discussed for various experimental configurations. It is shown that with a cicularly polarized pump beam, the polarization changes induced on a nearly collinear probe beam are due to this coherence effect only. In other configurations, this parametric coupling can appear as an additional contribution to the observed signal, especially when pump and probe are derived from the same laser beam. It is pointed out that this coupling can occur not only when the pump and probe beams are at the same wavelength, but also when the difference or the sum of their frequencies can excite a Raman or a two-photon resonance in the medium.

Optical Kerr effect in fiber gyroscopes: effects of nonmonochromatic sources

Abstract: The effects of source bandwidth on the optical Kerr effect are calculated. We show that the nonreciprocal Kerr bias error in fiber gyroscopes may be substantially reduced by using broadband sources.

Third order autocorrelation study of amplified subpicosecond laser pulses

Abstract: We have used the well-known optical Kerr effect shutter method to determine the temporal width and shape of subpicosecond pulses issued from a passively mode-locked CW dye laser, feeding a three stage amplifier. This technique corresponds to a third order correlation measurement and thus yields information on the pulse profile and especially about a possible asymmetry. The accuracy of results greatly benefits from the large dynamic range that reaches 103.

Magneto-optic storage media

Abstract: A magneto-optic storage media which utilizes two layers or films of magnetic material, with the magneto-optic hysteresis loop of one of the films being of a sense opposite to the sense of the magneto-optic hysteresis loop of the other film. The media permits the Farraday effect polarization rotations produced by one of the magnetic films to be in phase with Kerr effect polarization rotations produced by the other of the magnetic films, such that additive mode conversion is provided from different portions of the media whereby the detected signal has an increased signal-to-noise ratio.

Temperature dependence of the Kerr effect in a silica optical fibre

Abstract: The temperature dependence of the electro-optic Kerr effect has been measured in a silica-cored monomode optical fibre. The Kerr constant was measured as 5.3×10−16 mV−2 at 23°C with a temperature coefficient of +0.56% per deg C over the range 23 to 88°C. This measurement has implications for optical-fibre temperature and electric field sensors.

Use of modulation of elliptic light polarization for the study of electric birefringence of polymer solutions in pulse fields

Abstract: A compensation method was developed for measuring electric birefringence in the pulse field of constant and sinusoidal voltage which is based on the use of modulation of elliptic light polarization. The method enables the equilibrium Kerr effect and kinetics of electric birefringence of conductive polymer solutions to be examined.

Efficient femtosecond optical Kerr shutter

Abstract: Conjugated molecules, with large optical nonlinearities, are tested as materials usable for femtosecond optical Kerr shutter technique. With β‐carotene, in acetone solution, we have achieved responses limited by the 100‐fs width of the optical pulses and characterized by a resolution better than 1 ps with a dynamic range of 100.

Molecular electro-optics

Abstract: When fluids and molecular solutions are subjected to electric fields various optical properties undergo a change. Although the best known effect is that of electric birefringence (the Kerr effect), other electro-optical phenomena such as scattering, optical rotation, dichroism and fluorescence all exist and have been used to study macromolecules. A brief account is given of representative electro-optical effects and how they can be measured and used for molecular characterisation. In recent years interest has been growing in the use of such electro-optical phenomena as possible optoelectronics switch and device phenomena.

Liquid-core optical fibre for voltage measurement using Kerr effect

Abstract: Liquid-core optical fibre for voltage measurement, based on the Kerr effect, is shown. The measurements are performed for 50 Hz alternating voltage, i.e. for 23?130 kV/m electric fields.

The magneto-optical polar Kerr effect and birefringence spectra in PrFeO3 between 2 and 5.6 eV

Abstract: The complex polar Kerr effect and the effect of birefringence in PrFeO3 are reported between 2 and 5.6 eV. It is shown that the birefringence observed in transmission has its origin in the electronic transitions involving 3d levels of Fe3+ which are situated in the near-ultraviolet spectral range. The low-energy Kerr ellipticity and the associated Faraday rotation in PrFeO3 are of opposite sign compared to the other orthoferrites studied so far. This situation is analogous to that observed in Pr3+ and Nd3+ substituted iron garnets. It is concluded that the mechanism responsible for the anomalous Faraday rotation in Pr3+ and Nd3+ iron garnets does not require the presence of tetrahedral iron ions.

Time‐resolved Brillouin spectra in a CO2 laser plasma interaction

Abstract: Kerr cell techniques have been used to obtain spectra at 10.6 μm of the radiation backscattered from a CO2 laser plasma interaction. The spectrum is strongly red‐shifted at high energies, with spectral modulation. These aspects of the backscattering suggest that the scattering is occurring from ion quasimodes produced by the strong coupling of the laser to the plasma.

Kerr effect in solid polymethylmethacrylate and polyethylene

Abstract: Commercial grade polymethylmethacrylate (PMMA) and polyethylene (PE) have been found to exhibit the Kerr effect. The Kerr constants were determined to be ∼0.2×10−14 m/V2 for PMMA (at room temperature) and ∼0.1×10−14 m/V2 for uncrosslinked low‐density PE (at 110 °C).

Degenerate four-wave mixing in p-type germanium: an absorbing medium

Abstract: We present the results of degenerate four-wave mixing (DFWM) studies in three samples of p-type Ge with a wide range of absorptive properties. Three mechanisms for DFWM are observed in this material. A model, which includes the mechanisms of the inhomogeneously broadened saturable absorption of p-type Ge and the optical Kerr effect that is due to bound electrons in Ge but not the mechanism of bulk plasma formation that occurs only at extremely high pump intensities, is developed and compared with the experimental results. Pump-beam attenuation by the medium is shown to be an important effect in modeling DFWM. The model, which has no free parameters, fits the experimental data well for samples with small-signal transmission of greater than 20%.

Measuring the Magnetooptic Kerr effect by diffraction

Abstract: A method is presented to measure the Magnetooptic Kerr Effect (MOKE) by diffraction. This is accomplished by giving the magnetized surface a magnetization distribution which functions like a linear diffraction grating. It is shown that the first and higher orders of the light diffracted by such a grating are produced by MOKE whereas the zero order approximately represents the reflectivity of the surface (given by the Fresnel formulae assuming zero magnetization). The procedure used here to form a grating is restricted to thin soft magnetic films, and has been demonstrated on evaporated Fe-Ni films. It uses the magnetic field of a pulse-driven meandered stripe-conductor placed in close contact with the film in the presence of a homogeneous external magnetic field. Experimentally determined Kerr intensities were compared with those measured by ellipsometric methods. Good agreement was found in the case of films with uniaxial anisotropy. For films with no anisotropy, the relative dependence of Kerr intensity vs wavelength, polarisation and angle of incidence could be derived.

Optical distance-measuring instrument

Abstract: Optical distance-measuring instrument operating in accordance with the focusing measurement method, in accordance with which for the purpose of determining distance the focal point is displaced into the surface of a workpiece to be scanned. The displacement of the focal point is performed by material in the beam path, whose refractive behaviour can be changed under the influence of an electric or magnetic field. Use can be made, for example, of materials which change their refractive behaviour in accordance with the Kerr effect. The change in the refractive behaviour follows a change in the electric field virtually in phase and without inertia, so that very high measurement frequencies can be achieved which cannot be achieved using mechanically moved or controlled devices for displacing focal point.

Effet Kerr optique dans une fibre optique biréfringente multimode

Abstract: In this paper, we study the optical Kerr effect theoretically in multimode birefringent optical fibers in connection with the characteristics of the fiber and excitation conditions. We observe experimentally, for a pump power 2 W in the fundamental mode, 70% modulation depth for the probe light with multimodal coupling.

Driving method for optical shutter element

Abstract: PURPOSE:To reduce the degradation of characteristics when an optical shutter element utilizing a Kerr effect or the like as an electroptic effect is used continously for a long time, by applying positive and negtive voltages alternately to the same electrode terminal during opening of a shutter gate. CONSTITUTION:A Kerr effect as an electrooptic effect is utilized to form an optical shutter element. In case that this optical shuter element is driven, a pulse voltage where a positive voltage V' and a negative voltage V'' alternate in a time T'w and a time T''w is applied to the same electrode terminal during opening of a shutter gate (the time T'w= the time T''w= the half of the time of opening of the shutter gate). By this driving, the degradation of characteristics of the optical shutter element is reduced even if this optical shutter element is used continuously for a long time. In an optical shutter element utilizing the light scattering effect due to forced phase change, the similar effect is obtained.