Papers by Keyword: Faraday Rotation

Abstract: Optical and magneto-optical spectra in transmission and reflection and their features for microcavity one-dimensional magnetophotonic crystals with double layer bismuth-substituted iron garnet films are considered. At the first presented the experimental results of magnetic circular dichroism investigations in microcavity one-dimensional magnetophotonic crystals.

Abstract: The low-temperature behavior of optical and magneto-optical properties of microcavity 1D-MPCs with the Bi, Gd, Al-substituted YIG cavity layers of different compositions including compositions with a magnetic compensation temperatures were investigated. The optical transmittance and position of the resonant peaks in optical transmittance and the Faraday rotation spectra were found to be independent of temperature in all types of 1D-MPCs. The temperature dependence of changing the sign of Faraday rotation experienced the hysteresis with a value 8 K in one of two investigated MPCs with magnetic compensation temperature, while in the another MPC the hysteresis did not exceed 1 K. The possible origins of these properties are discussed.

Abstract: The design and measurement of Verdet constant of magneto optical fiber is reported. An optical beam was found that it linearly polarized at the fiber input changes to elliptically polarized after propagating down the fiber and an elliptical fitting method was studied and reported. Traditional method is based on circle polarized principle, rotation angle is obtained through manually adjust the polarizer which is rather inaccurate especially for small rotations. Through the development of elliptical fitting equations and the test of intensity on major and minor points, fiber Verdet constant can be measured more precisely. The measured data of TZN (TeO₂- ZnO-Na₂CO₃) fiber was verified and it provides improved accuracy compared with existing methods.

Abstract: An optical-electronic system for Faraday rotation measurement is designed and constructed to evaluate the verdet constant of magnetic -optical glasses. The works include the optical bench setup and development of software. PbO-Bi2O3-B2O3 glasses systems were fabricated and characterized by using the self-constructed optical bench and the obtained Verdet constants @632.8nm for glass PBB1 was verified by using a commercial powermeter (as detector). The developed measurement system showed characteristics of low cost, small size and accurate.

Abstract: In a continuing effort to develop a noninvasive means of monitoring glucose levels using many methods. In this paper a laser, closed-loop, system was designed and a model was developed to extract the glucose concentration information by Faraday rotation with Terbium Gallium Garnet Crystal(TGG Tb₃Ga₅O₁₂). The system was tested using various concentrations of glucose. The results show that for a static, non-moving sample, glucose can be predicted. For the physiologic range (0-16mmol/l) for either laser wavelength (523nm or 632.8nm), the Correlation coefficient value (R2) are 09977and 0.9995 respectively. The measurement results of 24 hours show the system with good stability, which error is less than 0.05%.

Abstract: The peculiarities of the Faraday rotation in the imperfect garnet-type crystals for which the lattice irregularities are represented by the mixed valence clusters of transition metal ions are analyzed. The model takes into account the cubic and low symmetry crystal fields acting on the metal ions and migration of the “extra” hole. The electric dipole transitions in these types of clusters with migrating hole coupled to the spin core through the double exchange mechanism are shown to lead to a significant magnetooptical activity in the visible range of spectrum. The intensity of these transitions can be comparable or higher than those for the magnetic dipole ones in the same range of frequencies.

Abstract: Faraday rotation (FR) and magnetic circular dichroism (MCD) of nanocomposite structures based on potassium-aluminum-germanium-boron glasses co-doped with Fe and rare earth (RE) or Y+Bi oxides have been studied. Formation of magnetic nanoparticles as a result of the glass heat treatment ensures them magnetic and magneto-optical properties typical of magnetically ordered substances. At the same time, glasses keep transparence in visual spectral range owing to low paramagnetic oxides concentration. FR and MCD spectra of the heat treated glasses are shown to be very close to those of γ-Fe2O3 and practically independent of the RE element nature for the light wave energies lower than 22000 cm-1. For higher energies, the MCD spectrum shape depends strongly on RE what evidences the different origin of magneto-optical effects in two spectral ranges.

Abstract: Nano-composite structures based on potassium-aluminum-germanium glasses doped simultaneously with Fe and rare earth (RE) oxides - Gd, Tb, Dy, Ho, or Yb were studied for the first time. Samples were fabricated by glass technology and subjected to an additional thermal treatment at different regimes. Formation of magnetic nanoparticles was revealed with transmission electron microscope. Morphology and space distribution of nanoparticles in the glasses as well as optical and magneto optical spectra have been shown to be dependent on the additional treatment regime and almost independent of the type of the rare earth element.

Abstract: Сomposite films containing II-VI based semiconductor nanoparticles have been prepared by different physical and chemical techniques. Non-magnetic CdS1-xSex nanoparticles were grown by melting of the semiconductor doped fine powder borosilicate glass. The composite semimagnetic semiconductor Cd1-xMnxTe based films were fabricated by embedding in SiO2 matrix with using of pulsed laser deposition technique. New chemical approach to synthesis of Cd1-xMnxS nanoparticles in polymer matrix has been proposed. The optical absorption edge for CdS1-xSex , Cd1-xMnxTe nanoparticles and exciton structure in the spectrum of Cd1-xMnxS nanoparticles shifted to the higher-energy side compared to those for bulk crystals due to the quantum confinement effect. Magneto-optical Faraday effect for non-magnetic semiconductor nanoparticles in glass demonstrates only small changes as compared with that of bulk semiconductors. The revealed peculiarities in spectral and magnetic field dependences of the Faraday rotation for the studied semimagnetic semiconductor composite films can be attributed to the influence of dimensionality on spin exchange parameters for such kind of nanostructures.

Abstract: Magnetic-optical film (hereafter, MO film) is a bismuth-doped iron garnet film grown on a gadolinium gallium garnet substrate by liquid phase epitaxial method. Because an MO film has physical characteristics such as Faraday rotation and magnetic anisotropy, the distribution of its external magnetic field can be visualized. The MOI (Magneto-Optic/Eddy Current Imager) was developed to detect far-side cracks and corrosions in aluminum alloy materials on an aircraft. The detection probability of 2.5mm-length cracks is 90/95% when the MO film and the induced area current are used. However, the quantitative evaluation algorithm for quantifying crack shapes and sizes has yet to be proposed. This paper investigates a quantitative evaluation algorithm for magnetic optical eddy current imaging by using the finite element analysis methods (FEM) and experimental results. The MOI including a primary induction coil was simulated by FEM software. The position, depth, shape, and the induction current frequency, lift-off were simulated and examined. A simplified quantitative evaluation algorithm for MOI is proposed by using the analysis results.