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[IEEE 2018 International Multi-Conference on Industrial Engineering and Modern Technologies (FarEastCon) - Vladivostok, Russia (2018.10.3-2018.10.4)] 2018 International Multi-Conference on Industrial Engineering and Modern Technologies (FarEastCon) - Modeling of the Magneto-Optical Channel of a Fiber-Optic Displacement Sensor
摘要： According to earlier studies conducted by the authors it was found that contactless fiber-optic sensors based on the magneto-optical Faraday effect (FOSF) in epitaxial films of iron garnet can be used for contactless monitoring of the status of control plate valves that regulate the flow of fire and explosion hazardous substances and operate over a wide temperature range. FOSF makes it possible to control the displacement and tilt angle of the valve regulating element (valve plate). However, at the moment there are no sufficiently accurate mathematical models for such FOSF. Studies have shown that the discrepancy between simulation results and experiments can reach 105%. The discrepancy between the results increases significantly when the FOSF is operated in a wide temperature range (from minus 196 to +80 °C). The low accuracy of the FOSF models does not make it possible to develop efficient means of compensating its intrinsic and complementary errors. The existing FOSF models are not sufficiently accurate, since they do not take into account: the distribution of the normal component of the magnetic field strength along the magneto-optical element (MOE) cross-section; the distribution of the optical radiation intensity along the MOE cross-section; optical absorption of the FOSF optical elements. According to the results of research carried out by the authors a set of mathematical models that takes into account the nonuniform distribution of the optical radiation intensity along the MOE cross-section, the nonuniform distribution of normal component of the magnetic field strength along the MOE cross-section, the optical absorption in FOSF optical elements and their temperature dependences was developed. This allowed us to significantly reduce the modelling error. The discrepancy between the results of mathematical modeling and experimental studies of FOSF prototypes does not exceed 7.2%.
关键词： control valve,contactless fiber optic sensor,mathematical model,fire and explosion safety,Faraday effect
更新于2025-09-23 15:23:52
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Micromagnetic Modeling of All-Optical Switching
摘要： The control of the magnetization at the microscale by pure optical means is fundamentally interesting and promises faster speeds for data storage devices. Although several experiments have shown that it is possible to locally reverse the magnetization of a ferromagnetic system by means of laser pulses, a completely theoretical description of these all-optical switching (AOS) processes is still lacking. Here, we develop an advanced micromagnetic solver that is applied to the numerical study of the AOS. The solver is based on the Landau–Lifshitz–Bloch equation that governs the dynamics of the magnetization coupled the microscopic three-temperature model, which describes the temporal evolution of the temperatures of the subsystems as caused by laser heating. The helicity-dependent magnetization switching is evaluated by a magnetooptical effective field caused by the inverse Faraday effect when a circularly polarized laser is applied to the sample. All the other usual terms of a full micromagnetic model are included (exchange, anisotropy, and Dzyaloshinskii–Moriya interaction). As a test, the model is used to describe the local magnetization switching of thin-film samples with high perpendicular anisotropy. The results are in a good agreement with available experimental observations.
关键词： Landau–Lifshitz–Bloch (LLB) equation,three temperatures model (3TM),inverse Faraday effect (IFE),micromagnetism,All-optical switching (AOS)
更新于2025-09-23 15:22:29
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EuF2-based crystals as media for high-power mid-infrared Faraday isolators
摘要： This letter presents the investigation of spectral, magneto-optical and thermo-optical characteristics of cubic EuF2 +x solid solution crystals. The dispersion of the Verdet constant measured in the wavelength range of 532–1940 nm demonstrates that such crystals can be used for creating Faraday isolators for the wavelength of ~2 μm. The optical anisotropy parameter of EuF2+x crystals is negative, which means that there exists a dedicated orientation of the crystallographic axes at which thermally induced depolarization may be reduced substantially. The performed research shows that an EuF2 crystal is highly promising for the development of Faraday isolators for high-power mid-IR lasers.
关键词： Thermo-optic effects,Magneto-optical materials,Faraday effect
更新于2025-09-23 15:21:21
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Light-induced magnetism in plasmonic gold nanoparticles
摘要： Strategies for the ultrafast optical control of magnetism have been a topic of intense research for several decades because of the potential impact in technologies such as magnetic memory, spintronics and quantum computation, as well as the opportunities for nonlinear optical control and modulation in applications such as optical isolation and non-reciprocity. Here we report experimental quantification of optically induced magnetization in plasmonic gold nanoparticles due to the inverse Faraday effect. The induced magnetic moment is large under typical ultrafast pulse excitation (<1014?W?m?2 peak intensity), with magnetization and demagnetization kinetics that are instantaneous within the subpicosecond time resolution of our study. Our results support a mechanism of coherent transfer of angular momentum from the optical field to the electron gas, and open the door to all-optical sub-wavelength strategies for optical isolation that do not require externally applied magnetic fields.
关键词： ultrafast optical control,quantum computation,inverse Faraday effect,spintronics,magnetic memory,plasmonic gold nanoparticles,light-induced magnetism
更新于2025-09-23 15:19:57
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - N-Matrix Jones Analysis of a Fiber-Optic Current Sensor
摘要： Fiber-optic current sensors (FOCS) based on Faraday effect could potentially be exploited in several high voltage applications where the electromagnetic immunity is a mandatory requirement. Nevertheless their actual in-field exploitation has always been limited due to critical issues such as fiber residual birefringence that degrades the current measurement accuracy. To this purpose special low-birefringence fibers and spun fibers featuring minimal residual birefringence have been developed. Yet these solutions do not prevent the birefringence contribution induced by the curvature arising during the realization of the current sensing coil. In the present work a novel numerical simulator based on the N-matrix Jones formalism [1] has been developed to analyse the detrimental effect of the birefringence on the Faraday-induced rotation of the state of polarization (SOP) of the light inside a FOCS due to the presence of an electrical current. In particular, the simulator takes into account both the intrinsic fiber birefringence and the bending-induced birefringence [2], combined with the circular birefringence caused by the Faraday effect. Simulation results have evidenced interesting behaviors related to the dependence of the effective Verdet constant Veff on both the number N of turns of the sensing fiber coil and the coil curvature radius r. Indeed Veff represents the FOCS effectiveness in inducing a polarization rotation theta, which is directly proportional to the electrical current I according to: ? = 2Veff (N ,r) ? N ? I . (1) In particular, simulations have shown that increasing N the values of Veff reduce due to the presence of intrinsic and bending-induced birefringence. This implies that the FOCS effectiveness does not grow linearly with N. A same trend also occurs when the coil radius r is progressively reduced. The simulation results have also been experimentally validated with the polarimetric setup shown in Fig. 1(a). The FOCS has been realized by wrapping a standard single-mode ?bre around an electrical cable supplied with an AC current up to a rms value of 35 A at the frequency of 50 Hz. A linearly polarized laser at 1.55 μm is coupled to the fiber coil through a circulator and reflected back to the receiver by a Faraday rotator mirror (FRM). This FRM cancels out all the reciprocal birefringence effect in the retracing path, while maintaining the Faraday rotation to be measured [3,4]. At the receiver side the orthogonal components of the SOP of the light are analyzed by means of a polarizing-beam splitter (PBS) together with a pair of photodiodes (PD1, PD2) and the Faraday-induced rotation is recovered.
关键词： Fiber-optic current sensors,Faraday effect,N-matrix Jones formalism,Verdet constant,birefringence
更新于2025-09-16 10:30:52
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Vertical Displacement of the Magnetooptical Hysteresis Loop in the Magnetoplasmonic Nanocomposite
摘要： The results of synthesis and investigation of magnetooptical (MO) properties of thin-film magnetoplasmonic nanocomposite, which is a layer of bismuth-substituted iron garnet Bi:YIG with plasmon nanoparticles Au, have been presented. The effect of vertical displacement of the MO hysteresis loop relative to the origin has been found in the study of MO-properties in the process of reversal magnetization of this magnetoplasmonic nanocomposite. It has been shown that the observed effect is most pronounced in the vicinity of the localized plasmon resonance in the system of metal nanoparticles that are part of the magnetoplasmonic composite.
关键词： magnetooptics,nanocomposite,nanoparticle,Faraday effect,thin film,plasmon resonance
更新于2025-09-16 10:30:52
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Nonreciprocal propagation in optical fibers
摘要： Nonreciprocal propagation in optical fibers presents practical interest. The present work treats the problem of nonreciprocal propagation in nonabsorbing cylindrically layered structures at axial magnetization characterized by magnetooptic electrical permittivity, ?ε, and magnetic permeability, ?μ, tensors, using transverse circularly polarized representation. The solutions to the vector Helmholtz equation are expressed analytically as functions of circular cylindrical coordinates (cid:37), ?, and z. The results are applied to a magnetooptic circular cylindrical waveguide and illustrated on fiber waveguides with an yttrium iron garnet (YIG) core and a cladding formed by gallium substituted yttrium iron garnet (GaYIG) at the optical communication wavelength of 1.55 μm. The propagation distance in the waveguide for a π/4 azimuth rotation of a transverse linearly polarized incident wave on the waveguide axis required in isolators is about 100 μm.
关键词： magneto-optical effect,Faraday effect,isolator,nonreciprocity
更新于2025-09-12 10:27:22
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Fabrication and magneto-optical properties of TGG transparent ceramics
摘要： Terbium gallium garnet (Tb3Ga5O12, TGG) transparent ceramics were synthesized by the co-precipitated method and vacuum sintering with MgO as sintering aids. Samples sintered at 1500℃, 1550℃ and 1600℃ for 20h were utilized to examine the phase compositions, optical quality, microstructure and magneto-optical property. X-ray diffraction (XRD) results show that the three samples have pure garnet crystal structure. The sample sintered at 1550℃ shows high transparency and the optical transmittance is close to 80% in the region of 500-1500 nm. SEM micrographs demonstrate that the sample sintered at 1550℃ exhibit best microstructure and the average grain sizes were 5.32 μm. The Verdet constant of the samples were investigated in detail at different wavelength and temperature. The results indicated that TGG ceramics can meet the demand for magneto-optical devices in the visible-near infrared region.
关键词： Faraday effect,Magneto-optical properties,TGG ceramics,Optical materials
更新于2025-09-10 09:29:36
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Fabrication of Ferromagnetic Co–MgF <sub/>2</sub> Granular Film With High Transmittance and Large Faraday Effect for Optical Magnetic Field Sensor
摘要： In the magneto-optical devices and sensors using the Faraday effect, maintaining the transmitted light intensity of a Faraday element is a key issue. A granular ?lm with ferromagnetic ?ne metals dispersed in an insulator matrix has been expected to have both high transmittance and large Faraday effect. In this paper, we fabricated the Co–MgF2 granular ?lm prepared by co-evaporation and investigated the effect of substrate heating temperature during co-evaporation and post-annealing on the transmittance and the Faraday rotation of the granular ?lm. The Co–MgF2 granular ?lm deposited at high substrate temperature was exhibited like a ferromagnetic behavior and high transmittance. Also, we found that the ?gure of merit [deg./dB], which was de?ned as a ratio of a Faraday rotation angle and decay of the transmitted light, was improved by post-annealing.
关键词： Faraday effect,Co-evaporation,granular ?lm,optical magnetic ?eld sensor
更新于2025-09-09 09:28:46
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Separability of Systematic Effects in Polarimetric GNSS Radio Occultations for Precipitation Sensing
摘要： The Global Navigation Satellite System (GNSS) polarimetric effects on the propagation of radio occultations (ROs) are studied here. Polarimetric ROs have been suggested as a technique to detect heavy rain events using opportunity signals from GNSS satellites. The systematic effects that hinder the isolation of the precipitation information are described and their signi?cance and separability are assessed. A method that relies on the received phase difference between polarizations is presented. A dual-frequency extension is capable to completely separate the hydrometeor information from the other effects, including the ionospheric in?uence.
关键词： microwave propagation,Faraday effect,rainfall effects,radio occultation (RO),polarimetry,Global Navigation Satellite System (GNSS)
更新于2025-09-04 15:30:14