Verdet Constant Research Articles

Production and characterization of highly transparent novel magneto-optical Ho2Zr2O7 ceramics with anion-deficient fluorite structures

Based on material design idea, we employ a co-precipitation strategy to obtain sinterable Ho2Zr2O7 fluorite particles, successfully leading to novel transparent Ho2Zr2O7 ceramics with good optical/magneto-optical properties. The resulting precipitation precursor is identified to be hydrated basic carbonate upon calcination at the optimum temperature of 1250 °C into near-spherical Ho2Zr2O7 nanopowder with an average size of ∼64 nm and unimodal narrow size distribution. The crystal intrinsic oxygen defect in fluorite ceramic generally exists in the form of F+ center. The best bulk specimen achieved in this work exhibits a high refractive index of ∼2.1 and a high transparency of ∼74.4% at 1000 nm comparable with the corresponding defect-free single crystal (∼76.4% in theory). In the Ho2Zr2O7 structure system, the electronic polarizability of O2− anion generally remains constant around 2.2 Å3 in the visible region and the corresponding optical basicity is approximately 0.9. The developed magneto-optical transparent Ho2Zr2O7 ceramic has Verdet constants of -180 ± 3, -157 ± 5, -87 ± 2, -54 ± 2, and -43 ± 2 rad T−1 m−1 at 515, 635, 780, 980, and 1064 nm, respectively, which are roughly 1.2-fold higher than the commercial TGG crystal.

Faraday effect and refractive index of some imidazolium-based room-temperature ionic liquids and magnetic ionic liquids

Knowledge of the Faraday effect (FE) is very important in fundamental research and applications. Here, we report FE and refractive index studies for two magnetic ionic liquids (MILs), namely 1-ethyl- and 1-butyl-3-methylimidazolium tetrachloroferrate. Similar studies are also conducted for ionic liquids (ILs) that have a diamagnetic counteranion in place of [FeCl4]. The magnitudes of the Verdet constants of MILs are comparable and exhibit a negative sign. Furthermore, they are about one order larger than those of ILs with a diamagnetic counteranion of a positive sign. The Verdet constant shows monotonic variations as a function of wavelength in the range from 450 to 650 nm and is mainly related to charge transfer transitions in [FeCl4], with bands located in the UV region, though the contribution of d-d transitions in Fe+3 is negligible. A model for describing the measured Verdet constant data as a function of wavelength and temperature is given with respective values of effective Faraday A-, B-, and d-terms. The introduction of an empirical rule allows the estimation of Verdet constants of iron and imidazolium derivative based MILs, which are in some cases very high, thus indicating their potential in photonics applications. Imidazole shows a positive and nearly-two orders lower magnitude of the Verdet constant. The mixture of an MIL and acetonitrile allows the tuning of both the Verdet constant and the refractive index. The refractive indices, thermo-optic coefficients, and electronic polarizabilities of MILs are higher than those of ILs with a diamagnetic counteranion.

Fine-Grained Tb3Al5O12 Transparent Ceramics Prepared by Co-Precipitation Synthesis and Two-Step Sintering

In recent years, transparent terbium aluminum garnet (TAG) ceramics have attracted much attention for use in high-power Faraday isolators. Fine-grained ceramics usually possess better mechanical properties and accordingly better service performance. In this work, transparent TAG ceramics with fine grains were prepared using a two-step sintering procedure based on the low-temperature sintering process to suppress grain growth. The composition of TAG precursor and powders calcined at different temperatures was studied in detail. The microstructure and relative density of air pre-sintered TAG ceramics were studied to meet the requirements of hot isostatic pressing (HIP) post-treatment. Driven by the low pre-sintering temperature in air, the average grain sizes of the obtained TAG ceramics after HIP treatment are about 2.9–5.3 μm. The TAG ceramics (1.2 mm thick) pre-sintered at 1450 °C with HIP post-treatment at 1550 °C for 3 h under a 176 MPa Ar atmosphere possess the highest in-line transmittance of 80.3% at 1064 nm. The Verdet constant of the TAG ceramics at 632.8 nm is −180.5 rad·T−1·m−1 at room temperature, which is about 1.3 times larger than that of the commercial Tb3Ga5O12 single crystals.

Miniaturized double transit magnetic field measurement probe using the Faraday rotation principle.

This paper presents the design and experimental results of a double transit magnetic field measurement probe based on the Faraday rotation principle using terbium doped borosilicate glass as a sensor element. When the magnetic field is applied in the direction of propagation of light through the glass, the Faraday effect produces non-reciprocal circular birefringence. This property of the Faraday effect adds rotations when the light beam is reflected using a mirror placed at the other end of the glass and passed through the glass, making double transit of light through the sensor element. Experiments were carried out to verify the characteristics of the designed probe by inserting it inside the solenoid load coil. The Verdet constant of the glass is determined using the slope of the linear least-squares fitted curve between the Faraday rotation angle and the applied magnetic field, obtained as 89.22r a d/(T⋅m) with a relative uncertainty of 2.43%. The magnetic field was measured with 0.28% accuracy. In the optics experiments, alignment of components is the major task. To the authors' knowledge, this is the first of its kind double transit miniaturized magnetic field measurement probe configuration in which components are aligned inside the single probe structure. The probe is easily portable and can be used in inaccessible locations in various applications such as accelerators, Z/θ pinch devices, or fusion reactors such as tokamaks, in which the magnetic field is one of the main parameters.

Optical properties and Faraday magneto-optical effects of highly transparent novel Tb2Zr2O7 fluorite ceramics

A novel magneto-optical transparent Tb2Zr2O7 ceramic with a high in-line transmittance of ∼76.2% at 635 nm (∼98.2% of the theoretical transmittance of perfect Tb2Zr2O7 single crystal) was successfully fabricated by vacuum sintering from its solid-phase reactive fluorite particle. In the visible region, the Tb2Zr2O7 bulk material was found to have a high refractive index of around 2.10 ± 0.03 and an optical basicity of 0.985 ± 0.015 while the electronic polarizability of the O2− anion in the Tb2Zr2O7 system generally remained constant at 2.45 ± 0.06 Å3. The Faraday effect results revealed that the transparent Tb2Zr2O7 ceramic had Verdet constants of −400 ± 4, −260 ± 4, and −62 ± 2 rad·T−1·m−1 at 515, 635, and 1064 nm, respectively, which were roughly 1.9-fold higher than the commercial Tb3Ga5O12 single crystal. Our outcomes demonstrated that the developed optical functional Tb2Zr2O7 ceramic has potential application as an excellent magneto-optical material.

Extensive study of magneto-optical and optical properties of Cd1−xMnxTe between 675 and 1025 nm

We determine Faraday rotations and measure the optical reflection and transmission from magneto-optical Cd1−xMnxTe crystals with various stoichiometric ratios. For wavelengths between 675 and 1025 nm, we derive Verdet constants, optical loss coefficients, and the complex indices of reflection that are relevant measures to find suitable stoichiometric ratios of Cd1−xMnxTe for the realization of miniaturized optical isolators. By reflection and transmission measurements, we determine the stoichiometric ratios of several different Cd1−xMnxTe crystals and discuss the observed dependence of the optical properties on the stoichiometric ratio with respect to their use in optical isolators. Finally, we show the relevant figure of merit, i.e., the ratio of Verdet constants and optical loss coefficients for Cd1−xMnxTe crystals with Mn contents ranging from x = 0.14 to x = 0.50.

Preparation and properties of novel (Tb1−xCex)3Sc2Al3O12 magneto-optical transparent ceramics with different doping concentrations

(Tb1−xCex)3Sc2Al3O12 ceramics exhibited good optical quality and high Verdet constants, and were successfully prepared and optimised by Ce doping.

High Verdet Constant Glass for Magnetic Field Sensors

Due to the high transparency, high Verdet constant, as well as easy processing properties, rare-earth ion-doped glasses have demonstrated great potential in magneto-optical (MO) applications. However, the variation in the valence state of rare-earth ions (Tb3+ to Tb4+) resulted in the decreased effective concentration of the paramagnetic ions and thus degraded MO performance. Here, a strategy was proposed to inhibit the oxidation of Tb3+ into Tb4+ as well as improve the thermal stability by tuning the optical basicity of glass networks. Moreover, the depolymerization of the glass network was modulated to accommodate more Tb ions. Thus, a record high effective concentration (14.19 × 1021/cm3) of Tb ions in glass was achieved, generating a high Verdet constant of 113 rad/(T·m) at 650 nm. Lastly, the first application of MO glass for magnetic field sensors was demonstrated, achieving a sensitivity of 0.139 rad/T. We hope our work provides guidance for the fabrication of MO glass with high performance and thermal stability and could push MO glass one step further for magnetic sensing applications.

Effect of ZrO2 Content on Microstructure Evolution and Sintering Properties of (Tb0.7Lu0.3)2O3 Magneto-Optic Transparent Ceramics

In this paper, (Tb0.7Lu0.3)2O3 magneto-optical transparent ceramics with different ZrO2 doping levels (0~5 at%) were prepared by hydrogen sintering and sequential HIP technique using ZrO2 as a sintering aid. The effect of ZrO2 doping content on the microstructure and optical properties of (Tb0.7Lu0.3)2O3 ceramics was analyzed. We found that the optimal doping content of ZrO2 was 3 at%. The transmittance of 3 at% ZrO2-doped (Tb0.7Lu0.3)2O3 ceramics at the wavelength of 1064 nm was 74.84 %, and the Verdet constant was approximately 275.28 rad·T−1·m−1 at the wavelength of 650 nm.

Temperature-Monitored Fibre Optic Current Sensor Using Channelled-Spectrum Analysis

The fibre optic current sensor demonstrated here uses the intrinsic temperature and wavelength dependence of the Verdet constant of a terbium gallium garnet (TGG) magneto-optic material and the two micro-optic linear polarizers attached, to simultaneously extract the values of temperature and the optical Faraday rotation (induced by the presence of the magnetic field due an electric current on a conductor) without any extra optical component attached to the optical sensor head. The simultaneous measurement is achieved by illuminating the sensor head with a broadband optical source and by careful signal processing of the originated channelled-spectrum, compensate the sensor’s temperature dependence.

Impact of Sm ions on microstructure and magneto-optical effects of Y2O3 ceramics obtained by arc plasma melting

Faraday materials based on transparent ceramics are regarded for high power magneto-optical isolators. Pure yttria ceramics with high transmittance were prepared using the raw oxide powders. To enhance the magneto–optical performance of the ceramics, samarium oxide were introduced to yttrium oxide matrix as a paramagnetic ions. The Sm-Y2O3 Faraday ceramic was melted above 2700 °C for 10 min. It is noted that as-prepared ceramic presents the highest in-line transmittance above 61.0% at the high spectrum range of wavelengths from 350 to 1110 nm. Physicochemical properties of the sample were characterized by means of numerous techniques. No secondary phase was detected from the sample using X-ray diffraction. The Verdet constant of Sm-Y2O3 ceramic at 532 nm is as high as 20 rad/m*T, which is higher than that of pure Y2O3 ceramic. The good optical quality and magneto-optical properties make Sm-Y2O3 ceramic an attractive magneto-optical material.

Effect of WO3 on physical and magneto-optical properties of TeO2–La2O3–WO3 glasses for magneto-optics application

The ternary TeO2–La2O3–WO3 glasses with a formula of (100 − y − x)TeO2–yLa2O3–xWO3 (y = 5 and 10 mol%; x = 10 to 25 mol%) were made by the melting and casting method for high Verdet constant diamagnetic magneto-optical (MO) materials in the application of MO devices operating at 1550 nm. The compositional effects of WO3 and La2O3 contents on key glass properties of thermal stability, Knoop hardness, optical transmission, and Verdet constant, were systematically studied for both series of glasses. High transparency level (T: >70 %) in the region from 0.4 to 5.2 μm and a high refractive index (n: 2.05 at 1550 nm) were obtained in the studied glasses. The tellurite glasses with 5 mol% of La2O3 exhibited higher thermal stability and refractive indices than those with 10 mol% La2O3. The 85TeO2–5La2O3–10WO3 glass exhibited a large Verdet constant value of 3.95 rad/(T·m) at 1550 nm among the studied glasses. These results show that the presented TeO2–La2O3–WO3 glasses have considerable potential as diamagnetic MO materials for MO device applications operating at 1550 nm.

Fabrication of 4 at.% La3+ ion doped (TbxLu0.96−x)2O3 transparent ceramics by using NC-PLSH technology and characterisation of their magneto-optical properties

Nanocrystalline powders and pressureless sintering (NC-PLSH) were used in a H2 atmosphere to fabricate 4 at.% La3+ doped (TbxLu0.96−x)2O3 magneto-optical transparent ceramics. La3+ was utilised as a sintering aid, and Lu3+ was used as a phase stabiliser. A component of the (TbxLu0.96−xLa0.04)2O3 magneto-optical material was designed and investigated based on powder sinterability and green compact sintering. Transparent (TbxLu0.96−xLa0.04)2O3 ceramics were obtained by using a one-step sintering process in H2 atmosphere, without the need for subsequent hot isostatic pressing. The in-line transmittance of the as-polished 4 at.% La3+:(Tb0.8Lu0.16)2O3 ceramic was 79% at 1400 nm. The measured Verdet constant at wavelengths of 633 nm and 1064 nm was 354 rad/(T·m) and 100.2 rad/(T·m), respectively. The required length of the (Tb0.8Lu0.16La0.04)2O3 ceramics was 63% less than that of Tb3Ga5O12 ceramics.

Effect of La2O3 on the microstructure and optical performance of (Tb0.8Y0.2-xLax)2O3 ceramics

(Tb0.8Y0.2-xLax)2O3 transparent ceramics were prepared by using co-precipitation method combined with pressure-less sintering in flowing H2 atmosphere. Microstructure, optical transmittance, elements composition, and Verdet constant of the (Tb0.8Y0.2-xLax)2O3 ceramics were studied. The amount of La2O3 is crucial for the formation of expected transparent (Tb0.8Y0.2)2O3. With increasing content of La2O3, the number of pores and the grain size of as-fabricated (Tb0.8Y0.2-xLax)2O3 ceramics both decrease. When 4 at.% La2O3 is doped, the (Tb0.8Y0.16)2O3 transparent ceramics shows the highest transmittance of 73.3% at 1400 nm wavelength. With holding time increasing from 8 h to 15 h, the average grain size of (Tb0.8Y0.16La0.04)2O3 ceramics gradually increases from 5 μm to 13 μm. The Verdet constant measured at 633 nm is −352 rad/T·m, which is 2.63 times higher than that of TGG. In addition, large-size ceramics with Φ 20 mm × 3 mm and Φ 30 mm × 3 mm were also successfully obtained.

Faraday Angle and Accuracy Measurement of Magneto-Optic Current Transmission Based on New Telluride Glass

Two robust temperature-insensitive magneto-optical current sensor prototypes, based on double polarimetric processing schemes and single light way methods, were constructed using light reflection and light transition, respectively. A diamagnetism TeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -PbO-ZnO-BaF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> bulk glass was fabricated as a sensing head which, with/without a silver layer, acts as a mirror sputtered by RF sputtering. The Verdet constant of the TPZBF glass was measured using the self-made optical bench. The current sensors were evaluated under various currents and different temperatures. Results indicated that the constructed low-cost current sensor prototypes are accurate and stable for current sensing applications.

EPR NMR, and XPS study of LaAlO3 phase transition with enhanced magnetic and Faraday rotation properties in glass-ceramics

The phase transition of LaAlO3 in heavy metal oxide lead-tellurite glass was obtained and verified, along with its influence on glass structure, magnetic, and Faraday rotation properties were characterized through various techniques such as nuclear magnetic resonance (NMR), X-ray neutron diffraction, transmission electron microscopy, X-ray photoelectron microscopy, vibrating-sample magnetometer, and electron paramagnetic resonance (EPR). Cubic LaAlO3 nanocrystals were synthesized by one-pot hydrothermal technique and doped at 1, 5, 10, and 15 mol% into glasses, respectively. The LaAlO3 nanocrystals in as-casted glasses were characterized to be around 17 nm in cubic phase belonging to the Pm3m space group. After crystallization treatment at 360 °C for 2 h, cubic LaAlO3 phases were changed to 14–27 nm-rhombohedral phases due to the temperature-induced viscosity and strain in the melt. The phase transition yielded great modification to the glass structure through converting TeO4→TeO3, AlO6→AlO4, BO4→BO3, and producing non-bridging oxygen. The LaAlO3 doping enhanced the diamagnetism of as-casted glasses, but after phase transition, the weak diamagnetic nature was changed to strong ferromagnetism and the magnetization significantly increased with the LaAlO3 doping amount (Ms =55 emu/g). The mechanism behind magnetic property enhancement was discussed through 27Al NMR and EPR of glasses. The Verdet constant of glass with 10% LaAlO3 was greatly improved to 175 rad/ T.m at 633 nm which is much higher than the documented values in the literature.

Fabrication and characterizations of Tb3Al5O12‐based magneto‐optical ceramics

AbstractTransparent terbium aluminum garnet (TAG)‐based ceramics were fabricated by vacuum pre‐sintering and hot isostatic pressing (HIP) posttreatment from the co‐precipitated TAG powders with different stoichiometric ratios. After component optimization, the transparent ceramics with TAG single‐phase and attractive optical quality were obtained. The in‐line transmittance of optimal Tb(1+x)3(Al0.996255Si0.003745)5O12.0093625+3x/2 (x = −.004, −.002) ceramics (1.7‐mm thick) pre‐sintered at 1700°C for 20 h with HIP posttreatment at 1700°C for 3 h under 176‐MPa Ar reaches 82.6% at the wavelength of 1064 nm. With increasing terbium components, the secondary phase TAP appears in ceramics, which significantly degrades the optical quality of TAG‐based ceramics. The Verdet constant of the TAG‐based ceramics at 632.8 nm is about −181 rad T−1 m−1 at room temperature, which is about 33% higher than that of the TGG single crystals (−134 rad T−1 m−1).

A polarimetric fiber optic current sensor based on Bi12SiO20 crystal fluorescence

In this paper, we present a simple fiber optic sensor for magnetic-field/electric current measurement based on broadband fluorescence in a Bi12SiO20 crystal. A simple polarimetric scheme in combination with a standard 105/125 μm multimode fiber, a 405 nm laser diode and a spectrometer to analyze the spectrum is used. The magnetic field induces phase changes measured by the spectral shifts of the wavelength modulated response. The sensitivity is found to be wavelength dependent. It increases from 0.138 nm/A at 540 nm to 0.224 nm/A at 715 nm and is inversely proportional to the Verdet constant. A minimum current of 0.4A can be detected with a dynamic range of up to 32 dB. A detailed polarization analysis is presented.

Magnetic and magneto-optical properties of La0.8Sr0.2FeO3 crystals in alumina doped lead-bismuth-borate Faraday rotating glass matrix

In this study, we reported the synthesis of perovskite La0.8Sr0.2FeO3 nanocrystals in heavy metal oxide glass under the Al2O3 tailoring. 10 nm-nanocrystals of orthogonal La0.8Sr0.2FeO3 were synthesized and well distributed in glass by melting quenching followed with subsequent crystallization process at 400 °C for 30 min for 10% Al2O3 content. Aluminum abnormality effect and the Sr2+ induced multi-valence states of Fe ions and oxygen vacancies in La0.8Sr0.2FeO3 lattice, resulting in polarizability and oxygen packing density change. The glass with 10%Al2O3 amount exhibited a large thermal stability (132 °C) and significant enhancement in Verdet constant of 105 rad/T.m at 633 nm wavelength. The obtained Verdet constant values were compared with relative literatures and the values in this study are superior than values in literatures. The obtained glass with extremely good magnetic property and magneto optical performances can be promising candidate for photonics device applications.

Terbium (III) Oxide (Tb2O3) Transparent Ceramics by Two-Step Sintering from Precipitated Powder

As a result of preliminary air calcination and subsequent reduction in a flowing NH3 atmosphere of the precursor from the liquid precipitation method for the first time, pure-phase Tb2O3 powder with an average particle size of 135 nm was prepared. The Tb2O3 magneto-optical transparent ceramics with the average grain size of 1.3 μm were successfully fabricated by vacuum pre-sintering and hot isostatic pressing post-treatment from the as-synthesized Tb2O3 powder. In-line transmittance values of Tb2O3 ceramics reach 70.3% at 633 nm, 78.1% at 1064 nm, and 79.4% at 1400 nm, respectively. Thanks to the high intrinsic concentration of Tb3+, Tb2O3 ceramics present high Verdet constants of −427.3 and −123.7 rad·T−1·m−1 at 633 and 1064 nm, which are about 3.1 and 3.4 times higher than those of commercial Tb3Ga5O12 crystals, respectively. Due to the excellent magneto-optical properties, Tb2O3 ceramics are promising candidates for the development of Faraday isolator toward compaction used in visible and near-infrared bands.