Self-trapping in media with saturation of the nonlinear index.
Optical beams self trapping characteristics in molecular fluids with nonlinear intensity dependent index /orientational Kerr effect/ saturation
Brewer, R. G.↗
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Results for “KERR EFFECT”
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A study of transient stimulated Raman scattering and self-focusing in the picosecond time regime
Two third order processes, stimulated Raman scattering and self-focusing, with picosecond pulses are studied. In the case of transient stimulated scattering, the gain is reduced from the steady state value, and qualitatively new features, such as shortening and delay of the Stokes pulse relative to the laser pulse, appear. These predictions are extended to realistic laser pulses, and experiments confirm all of the theoretical predictions. The self-focusing and frequency broadening of picosecond pulses is studied in the absence of stimulated Raman scattering in several materials with large orientational Kerr constants. Measurements of the relaxation time indicate that the orientational Kerr effect is important in the self-focusing of picosecond pulses. Self-focused filaments are observed to propagate with constant diameters over a distance greater than 10 cm, but disappear before the end of a 20 cm cell. The filaments radiate light continuously along their path and the spectrum of the light shows that the frequency content extends symmetrically for several hundred wave numbers on either side of the laser frequency.
Reintjes, J. F.↗
Study of self-focusing and self-phase-modulation in the picosecond-time regime.
Study of the propagation of a single picosecond pulse of a mode-locked Nd-glass laser in CS2 nitrobenzene and toluene by observations of the birefringence and spectral changes in self-focused laser light. Multiple second-harmonic probing beams are used for birefringence measurements in a single IR pulse in various portions of the active cell. The orientational Kerr effect is found to be the prime factor of induced birefringence in nitrobenzene and toluene. The results for CS2 are also consistent with this mechanism and show that the duration of an IR pulse in the focal volume is less than that of the incident pulse. The properties of beams which are focused within the cell by an external lens are also investigated.
Reintjes, J.↗
Thermomagnetic recording and magneto-optic playback system having constant intensity laser beam control
A system is developed for maintaining the intensity of a laser beam at a constant level in a thermomagnetic recording and magneto-optic playback system in which an isotropic film is heated along a continuous path by the laser beam for recording. As each successive area of the path is heated locally to the vicinity of its Curie point in the presence of a controlled magnetic field, a magneto-optic density is produced proportional to the amplitude of the controlled magnetic field. To play back the recorded signal, the intensity of the laser beam is reduced and a Faraday or Kerr effect analyzer is used, with a photodetector, as a transducer for producing an output signal.
Lewicki, G. W.↗
Characterization of magneto-optical media
Amorphous rare earth-transition metal (RE-TM) alloys and compositionally modulated TM/TM films were characterized in terms of their magnetic, magneto-optic, and galvanomagnetic properties. The loop tracer, vibrating sample magnetometer (VSM), and Rutherford Backscattering (RBS) facility were used to characterize and analyze the various properties of these magneto-optical storage media. Kerr effect, ellipticity, coercivity, and anisotropy at various temperatures, magnetoresistance, and resistivity are among the properties measured in Co/Pt films, Co/Pd films, and TbFeCo films.
Hajjar, Roger A.↗
Measurement of the magnetic anisotropy energy constants for magneto-optical recording media
Measurement of the magneto-optical polar Kerr effect is performed on rare earth-transition metal (RE-TM) amorphous films using in-plane fields. From this measurement and the measurement of the saturation magnetization using a vibrating sample magnetometer (VSM), the magnetic anisotropy constants are determined. The temperature dependence is presented of the magnetic anisotropy in the range of -175 to 175 C. The results show a dip in the anisotropy near magnetic compensation. This anomaly is explained based on the finite exchange coupling between the rare earth and transition metal subnetworks.
Hajjar, R. A.↗
Disturbance, the uncertainty principle and quantum optics
It is shown how a disturbance-type uncertainty principle can be derived from an uncertainty principle for joint measurements. To achieve this, we first clarify the meaning of 'inaccuracy' and 'disturbance' in quantum mechanical measurements. The case of photon number and phase is treated as an example, and it is applied to a quantum non-demolition measurement using the optical Kerr effect.
Martens, Hans↗
Free-space confocal magneto-optical spectroscopies at milliKelvin temperatures
We describe the operation of a free-space confocal optical microscope operated in a dilution refrigerator. The microscope is installed on a cold insertable probe to enable fast sample exchange while the refrigerator is held at low temperatures. A vector magnet provides a 6 T field normal to the sample and 1 T fields at arbitrary angles. A variety of optical microscopies and spectroscopies, including photoluminescence, Raman, magneto-optical Kerr effect, and spin relaxometry measurements are described, and some of the challenges associated with performing these measurements at milliKelvin temperatures are explored.
Lawrie, Benjamin↗
Effects of higher-order Kerr nonlinearity and plasma diffraction on multiple filamentation of ultrashort laser pulses in air
The effect of higher-order Kerr nonlinearity on channel formation by, and filamentation of, ultrashort laser pulses propagating in air is considered. Filament patterns originating from multiphoton ionization of the air molecules with and without the higher-order Kerr and molecular-rotation effects are investigated. It is found that diverging multiple filaments are formed if only the plasma-induced defocusing effect is included. In the presence of the higher-order Kerr effects, the light channel can exist for a long distance. The effect of noise on the filament patterns is also discussed.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Advanced magneto-optical microscopy: Imaging from picoseconds to centimeters - imaging spin waves and temperature distributions (invited)
Recent developments in the observation of magnetic domains and domain walls by wide-field optical microscopy based on the magneto-optical Kerr, Faraday, Voigt, and Gradient effect are reviewed. Emphasis is given to the existence of higher order magneto-optical effects for advanced magnetic imaging. Fundamental concepts and advances in methodology are discussed that allow for imaging of magnetic domains on various length and time scales. Time-resolved imaging of electric field induced domain wall rotation is shown. Visualization of magnetization dynamics down to picosecond temporal resolution for the imaging of spin-waves and magneto-optical multi-effect domain imaging techniques for obtaining vectorial information are demonstrated. Beyond conventional domain imaging, the use of a magneto-optical indicator technique for local temperature sensing is shown.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Spatial Separation of Carrier Spin by the Valley Hall Effect in Monolayer WSe 2 Transistors
We investigate the valley Hall effect (VHE) in monolayer WSe 2 field-effect transistors using optical Kerr rotation measurements at 20 K. While studies of the VHE have so far focused on n-doped MoS 2 , we observe the VHE in WSe 2 in both the n- and p-doping regimes. Hole doping enables access to the large spin-splitting of the valence band of this material. The Kerr rotation measurements probe the spatial distribution of the valley carrier imbalance induced by the VHE. Under current flow, we observe distinct spin-valley polarization along the edges of the transistor channel. From analysis of the magnitude of the Kerr rotation, we infer a spin-valley density of 44 spins/μm, integrated over the edge region in the p-doped regime. As a result, assuming a spin diffusion length less than 0.1 μm, this corresponds to a spin-valley polarization of the holes exceeding 1%.
42 ENGINEERING↗
Quantum magneto-optics of the graphite family
The optical conductivity of graphene, bilayer graphene, and graphite in quantizing magnetic fields is studied. Both dynamical conductivities, longitudinal and Hall's, are evaluated analytically. The conductivity peaks are explained in terms of electron transitions. Correspondences between the transition frequencies and the magneto-optical features are established using the theoretical results. We show that trigonal warping can be considered within the perturbation theory for strong magnetic fields larger than 1 T. The semiclassical approach is applied for weak fields when the Fermi energy is much larger than the cyclotron frequency. The main optical transitions obey the selection rule with {Delta}n = 1 for the Landau number n, but the {Delta}n = 2 transitions due to the trigonal warping are also possible. The Faraday/Kerr rotation and light transmission/reflection in quantizing magnetic fields are calculated. Parameters of the Slonczewski-Weiss-McClure model are used in the fit taking the previous de Haas-van Alphen measurements into account and correcting some of them in the case of strong magnetic fields.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Investigation of the use of the Kerr magneto-optic effect for the measurement of magnetic fields, phase 2 Final report
Use of Kerr magnetooptical for measuring magnetic fields
Greene, F. S., Jr.↗
Controllable diffraction pattern in semiconductor quantum well based on quantum coherence
In this paper, we study properties of diffraction of a weak probe field interacting with a symmetric semiconductor quantum well that is coherently manipulated by a standing wave. Based on the theory of quantum coherent and of light diffraction, we can obtain distribution of the diffraction spectra of the probe field. We consider the influences of Kerr nonlinear effect on the diffraction pattern, and studies show the distribution of diffraction pattern can be controlled through choosing appropriate physical parameters of system. Kerr nonlinear effect can enhance the brightness of central pattern and improve the transmission efficiency of the incident beam. A controllable diffraction pattern has potential applications in some areas, such as design of quantum diffractive optical elements, grating imaging system, precision measurement and so on.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Direct measurement of the static and transient magneto-optical permittivity of cobalt across the entire M -edge in reflection geometry by use of polarization scanning
The microscopic state of a magnetic material is characterized by its resonant magneto-optical response through the off-diagonal dielectric tensor component ε xy . However, the measurement of the full complex ε xy in the extreme ultraviolet spectral region covering the M absorption edges of 3d ferromagnets is challenging due to the need for either a careful polarization analysis, which is complicated by a lack of efficient polarization analyzers, or scanning the angle of incidence in fine steps. Here, we propose and demonstrate a technique to extract the complex resonant permittivity ε xy simply by scanning the polarization angle of linearly polarized high harmonics to measure the magneto-optical asymmetry in reflection geometry. Because this technique is more practical and faster to experimentally implement than previous approaches, we can directly measure the full time evolution of ε xy (t) during laser-induced demagnetization across the entire M 2,3 absorption edge of cobalt with femtosecond time resolution. We find that for polycrystalline Co films on an insulating substrate, the changes in ε xy are uniform throughout the spectrum, to within our experimental precision. This result suggests that, in the regime of strong demagnetization, the ultrafast demagnetization response is primarily dominated by magnon generation. Here, we estimate the contribution of exchange-splitting reduction to the ultrafast demagnetization process to be no more than 25%.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Spin-carrier coupling induced ferromagnetism and giant resistivity peak in EuCd 2 P 2
EuCd 2 P 2 is notable for its unconventional transport: upon cooling the metallic resistivity changes slope and begins to increase, ultimately 100-fold, before returning to its metallic value. Surprisingly, this giant peak occurs at 18 K, well above the Néel temperature (T N ) of 11.5 K. Here, using a suite of sensitive probes of magnetism, including resonant x-ray scattering and magneto-optical polarimetry, we have discovered that ferromagnetic order onsets above T N in the temperature range of the resistivity peak. The observation of inverted hysteresis in this regime shows that ferromagnetism is promoted by coupling of localized spins and itinerant carriers. The resulting carrier localization is confirmed by optical conductivity measurements.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Kerr, Faraday, and magnetoelectric effects in MnBi 2 Te 4 thin films
The topological magnetoelectric effect (TME) is a characteristic property of topological insulators. In this paper, we use a simplified coupled-Dirac-cone electronic structure model to theoretically evaluate the THz and far infrared Kerr and Faraday responses of thin films of MnBi 2 Te 4 with up to N = 10 septuple layers with the goal of clarifying the relationship between these convenient magnetooptical observables and the TME. Here we find that for even N, the linear Kerr and Faraday responses to an electric field vanish in the low-frequency limit, even though the magnetoelectric response is large and approximately quantized.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Kerr metric, rotating sources, and Machian effects.
Interior solution constructions serving as Kerr metric sources noting shape, mass density and rotation rates
Hernandez, W. C., Jr.↗