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Magnetic and Spintronic Materials and Their Applications
Published in Song Sun, Wei Tan, Su-Huai Wei, Emergent Micro- and Nanomaterials for Optical, Infrared, and Terahertz Applications, 2023
Magneto-optic effect. Magneto-optic effect refers to physical interaction between magneticmaterials (or materials in magnetic field) and light. Magneto-optic effect in magnetic materials mainly includes Faraday effect, magneto-optic Kerr effect (MOKE), Cotton-Mouton effect, and Voigt effect. Faraday effect depicts the light polarization rotation when a light through a material under a magnetic field which is applied in the direction of light propagation. MOKE describes the polarization changes when a linearly polarized light reflected from magnetic (or spintronic) materials. Cotton-Mouton effect and Voigt effect are both magneto-birefringence effects, in which the birefringence occurs when a magnetic field is applied perpendicular to the direction of light propagation. Due to magneto-optic effect, the magnetic materials can modulate and manipulate the properties of light, such as amplitude, phase, polarization, and spectrum.
Crystals and Glasses
Published in Marvin J. Weber, and TECHNOLOGY, 2020
Merritt N. Deeter, Gordon W. Day, Allen H. Rose
The first magnetooptic effect was discovered by Faraday and is now commonly known as the Faraday effect. This phenomenon occurs when linearly polarized light propagates through a material exposed to a magnetic field aligned parallel to the direction of propagation of the light. Under these conditions, the plane of polarization (defined by the oscillations of the electric field vector) rotates by an amount proportional to the applied magnetic field (or in some materials, the magnetization). This action, which is depicted in Figure 9.1.1, is known as Faraday rotation and occurs in gases, liquids, and solids. The applied magnetic field may also cause the initially linearly polarized state to become ellip- tically polarized. This effect is known as Faraday ellipticity.
New Measurement and Diagnostic Technologies
Published in N. H. Malik, A. A. Al-Arainy, M. I. Qureshi, Electrical Insulation in Power Systems, 2018
N. H. Malik, A. A. Al-Arainy, M. I. Qureshi
The magnetic field and current measuring optical sensors are usually based on magneto-optic effect which was first observed by Michael Faraday 150 years ago and is commonly known as the Faraday effect. According to this effect, when a linearly polarized light ray propagates through a magneto-optic medium in the presence of an external magnetic field, it undergoes a rotation of the plane of polarization proportional to the strength of the magnetic field (H). The rotation angle Δθ (radians) is related to the magnetic field intensity H (ampere-turn/m) and interaction length L (m) by the following equation: () Δθ=μKv∫H→⋅dL→
High-sensitivity fiber optic magnetic field sensor based on lossy mode resonance and hollow core-offset structure
Published in Instrumentation Science & Technology, 2021
Xue-Peng Jin, Hong-Zhi Sun, Shuo-Wei Jin, Wan-Ming Zhao, Jing-Ren Tang, Chun-Qi Jiang, Qi Wang
Magnetic field sensing has been widely used in biological, medical, military, electrical and other fields. Hence the monitoring of magnetic fields is signficant. Compared with other magnetic field sensors, optical sensors offer small structure, light weight, and no electromagnetic interferences.[1–5] Consequently, a variety of optical fiber magnetic field sensors have been reported, including devices based on magnetostrictive materials[4,6,7] and the Faraday effect.[8] Yang et al.[7] reported a magnetic field sensor based on etched fiber grating on which a thin film of magnetostrictive material was deposited by a sputtering system. Nascimento et al.[8] described an erbium-doped fiber laser that detects an alternating magnetic field by measuring the laser intensity. The sensor consists of two partially overlapping narrow-band fiber Bragg gratings and a section of doped fiber fabricated in the Fabry-Perot interferometer. Sun et al.[6] used a fiber Faraday rotator and a fiber polarizer to form an all fiber optic magnetic field sensor. However, these sensors have limitations that include complex manufacturing processes and high cost.
Gyrotropic slab waveguide coupled silica microfiber-based magnetic field sensor
Published in Instrumentation Science & Technology, 2020
Conversely, sensors exploiting the Faraday effect, due to their inherent optical nature, provide large dynamic range up to several Tesla and wide frequency bandwidth from static to GHz and are generally preferred over other methods in electric power systems.[26,27] A typical implementation based on the Faraday effect is to detect the rotation of the polarization direction as the light in the fiber propagates across the applied magnetic field. However, the devices are usually quite bulky because of the small value of the Verdet constant of silica necessitating a fairly long fiber required to produce a detectable field-induced polarization rotation, making it unsuitable for localized magnetic field measurements.[28]Table 1 summarizes the main characteristics of these sensing configurations for performance comparison.
Tunable unidirectional light transmission in a graphene–metal hybrid metamaterial
Published in Journal of Modern Optics, 2019
Chunyu Li, Lu Liu, Xiangxiao Ying, Jimmy Xu, Zhijun Liu
The phenomenon of unidirectional light transmission has attracted a great deal of interest due to its potential applications in optical isolators, polarization transformers and optical interconnects (1). One typical way for realizing unidirectional light transmission is to break the time-reversal symmetry via the Faraday effect in the presence of static magnetization of medium (2,3). This method involves an external magnetic field or bulk magneto-optical materials, which comes with a limitation in device sizes and complexity and thus is not suitable for component miniaturization and integration. Besides the Faraday effect, optical nonlinearity has also been introduced as a way to break the time-reversal symmetry (4,5). However, it requires a strong field of the probe light, presenting a constraint in practical applications. Recently, the metamaterials, as a kind of artificially structured materials, have emerged as an alternative for obtaining unidirectional light transmission (6,7). In contrast to the nonreciprocal transmission in magneto-optical or nonlinear media, the unidirectional transmission in metamaterials is reciprocal in nature, and is caused by cross-coupling and polarization conversion of light. Prior studies have demonstrated a variety of metamaterial structures, such as the twisted split-ring resonators (8,9), bilayer nano-antennas (10,11) and trilayer metallic structures (12–14) among many others, which exhibited unidirectional transmission covering a broad electromagnetic spectrum from microwave to the infrared.