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Magneto-Optical Characterization Techniques
Published in David A. Cardwell, David C. Larbalestier, Aleksander I. Braginski, Handbook of Superconductivity, 2022
Anatolii A. Polyanskii, David C. Larbalestier
The Faraday effect in transmission mode allows one to observe the domain structure of transparent magnetic materials [19]. In Figure G3.5.1, the sample is taken to be transparent, magnetic and to exhibit the Faraday effect. Linearly polarized light is incident on the sample, and here the sample possesses three different domains of magnetization, M. The top two domains have anti-parallel magnetization vectors normal to the crystal surface, while the third domain has an in-plane magnetization vector. The entire domain structure can be observed by viewing through the analyser. The Faraday angle of rotation for diamagnetic or paramagnetic materials determining the intensity contrast of the image, αF, is proportional to the material-dependent Verdet constant V according to the relation αF=VBzd
Examples of the Design of Measurement Systems
Published in Robert B. Northrop, Introduction to Instrumentation and Measurements, 2018
A material’s Verdet constant increases with decreasing wavelength and with increasing temperature. When a Verdet constant is specified, the wavelength and temperature at which it was measured must be given. For example, the Verdet constant of distilled water at 20°C and 578 nm is 218.3°/(T × m) (Hecht 1987, Ch. 8). This value may appear large, but the length of the test chamber on which the solenoid is wound is 10 cm = 10−1 m, and 1 T = 104 gauss, so actual rotations tend to be <±5°. The Verdet constant for lead glass under the same conditions is about six times larger. Not all Verdet constants are positive; for example, an aqueous solution of ferric chloride or solid amber has negative Verdet constants.
Crystals and Glasses
Published in Marvin J. Weber, and TECHNOLOGY, 2020
Merritt N. Deeter, Gordon W. Day, Allen H. Rose
The temperature dependence of the Verdet constant in paramagnetic materials is primarily associated with the temperature dependence of the paramagnetic susceptibility (Equation 21). This inverse proportionality to absolute temperature is the prime disadvantage of using paramagnetic materials in many applications.
Some features of magneto-optics of cholesteric liquid crystals
Published in Journal of Modern Optics, 2021
A. H. Gevorgyan, S. S. Golik, N. A. Vanyushkin, A. V. Borovsky, H. Gharagulyan, T. M. Sarukhanyan, M. Z. Harutyunyan, G. K. Matinyan
Let us consider the reflection and transmission of light through a planar CLC layer, that has magneto-optical activity in an external magnetic field directed along the CLC helix axis (Figure 1). We assume that the tensors of dielectric permittivity and magnetic permeability have the form: where are the principal values of the local dielectric permittivity tensor in the presence of an external magnetic field, g is the parameter of magneto-optical activity depending on the Verdet constant and external magnetic field, as well as the incident light wavelength and dielectric permittivity of media, (here V is the Verdet constant, and B is the external magnetic field induction [33]). The Verdet constant, in its turn, depends on temperature [33]; a = 2π / p, p is the helix pitch in the presence of an external magnetic field. We consider the case of normal incidence, that is, when the light propagates along the z-axis of the helix.
Fabrication of ridge waveguide on the ion-implanted TGG crystal by femtosecond laser ablation
Published in Journal of Modern Optics, 2020
Jing-Yi Chen, Jie Zhang, Liao-Lin Zhang, Chun-Xiao Liu
Magneto-optical materials are critical for various optical devices such as optical isolators, optical circulators and optical modulators in the fields of fibre lasers, optical communications and so on [1,2]. As one of the most intriguing and commercialized magneto-optical materials, terbium gallium garnet (Tb3Ga5O12, TGG) crystal has attracted widespread attention because of its outstanding optical and magnetic properties in the visible and infrared spectral range [2]. The Verdet constant (describes the strength of the Faraday effect) and the thermal conductivity are superior in TGG crystal compared with magneto-optic glasses [3,4]. Specifically, the Verdet constant of the TGG crystal is 35 Rad T−1m−1 and thermal conductivity is 7.4 Wm−1K−1 [5,6]. Furthermore, TGG possesses low transmission loss, high laser damage threshold and low absorption coefficient [7,8]. By virtue of its advantages, TGG crystal has become a suitable candidate medium for creating Faraday effect devices. However, the traditional bulk Faraday isolators are hardly compatible with photonic integrated circuits [9]. In order to realize the integration, it is necessary to develop a waveguide-type optical device with host TGG crystal.
Gyrotropic slab waveguide coupled silica microfiber-based magnetic field sensor
Published in Instrumentation Science & Technology, 2020
Terbium-doped borosilicate glass (MR4, Xi’an Afoa Incorporation, China) was selected to be the gyrotropic slab because of it is a large Verdet constant (120 rad/T.m at 632.8 nm) (http://www.xaot.com/sdp/173803/4/cp-4304059/0/Magneto-Optical_Glass.html) which provides good magnetic field sensitivity. Moreover, since the refractive index of MR4 (∼1.75 at 632.8 nm) is higher than that of the silica fiber, it can act as an optical waveguide slab coupled with a microfiber. The size of MR4 is a thickness of approximately 200 μm and an approximately width of 3.5 mm.