High Verdet Constant Research Articles

Effect of Na2O on Verdet constant of Tb-doped magneto-optical glass

The terbium (Tb) ions doped magneto-optical glasses have attracted significant attention due to their high Verdet constant and excellent optical properties. In the Tb ions doped glass, +3 and + 4 valence states of Tb ions coexisted. However, only the +3 valence is favorable for magneto-optical performance. This study proposed a strategy to increase the concentration of Tb3+ ions (CTb3+) in the glass. The high optical basicity Na2O is beneficial for enhancing the Verdet constant. The lower melting temperature suppresses the oxidation of the Tb3+ to Tb4+, leading to the increase of CTb3+. As a result, the Verdet constant at 650 nm was achieved as high as 78.6 rad/(T·m), representing a 42.8 % improvement compared to glasses melted at 1450 °C. This approach avoids glass crystallization at high concentrations of Tb doping and provides a new solution for preparing high-performance magneto-optical glasses.

High Verdet constant of Tb2O3-doped TiO-B2O3-Al2O3-Na2O magneto-optical glass

Tb-doped magneto-optical (MO) glass is widely used in fiber optics, optical isolators, and modulators. However, only the paramagnetic Tb3+ ions exhibit significant MO effects, whereas the diamagnetism Tb4+ ions suppress the MO effects. Therefore, the valence state control of Tb ions is very critical to optimize MO performance. Here, a reduction strategy was introduced to adjust the Tb valence in glass to achieve the high MO effect. The TiO, which has low valence Ti2+ ions and good reducibility, was used to suppress the oxidation of Tb3+ to Tb4+ ions. In the TiO-B2O3-Al2O3-Na2O glass, 10 mol% TiO can increase the Verdet constant at 650 nm by 19%. With the further increase in Tb2O3 concentration, the Verdet constant reaches a high value of 117 rad/(T·m) at 650 nm, which is close to the Verdet constant of TGG crystal (121 rad/(T·m)). This work provides a new approach to increase the Verdet constant of MO glass.

Highly transparent Tb3Al5O12 ceramics for kilowatt‐level Faraday isolator

AbstractTb3Al5O12 (TAG) ceramics with high optical quality were fabricated successfully by a solid‐state reaction method combined with hot isostatic pressing (HIP) post‐treatment. The microstructure, optical transmittance, Verdet constant, and thermo‐optical properties were investigated. The obtained TAG ceramics showed a dense microstructure, and the in‐line transmittance reached 82.8% at 1070 nm after laser‐grade polishing. The Verdet constant of TAG ceramics was measured to be 50.9 rad·T1·m−1 at 1070 nm, which is higher than that of commercial Tb3Ga5O12 crystals. The Faraday isolator based on TAG ceramics can provide an isolation ratio of 30 dB with a laser power of more than 1 kW. With excellent optical quality, high Verdet constant, and maximum working power, TAG transparent ceramics are promising for applications of kilowatt‐level Faraday isolators.

Effective Faraday rotator based on the TbYO3 crystal with a high Verdet constant and a high thermal conductivity.

Facing the demand of high-power laser development, a high-quality magneto-optical crystal with a high Verdet constant and a high thermal conductivity is needed. Herein, an effective Faraday rotation based on a TbYO3 single crystal with a strong magneto-optical effect, grown by the laser floating zone method, is demonstrated for the first time, to the best of our knowledge. The TbYO3 crystal has the Verdet constant which is 2.16 times (106 rad·m-1 T-1) higher than that of the TGG crystal (49 rad·m-1 T-1) at 880 nm. Additionally, the TbYO3 crystal also has a thermal conductivity of 11.8 W·m-1·K-1 and a laser-induced damage threshold of 1.59 GW·cm-2. These advantages can allow the TbYO3 crystal to be an attractive magneto-optical material.

Sagnac Magnetic Field Sensor Based on Sinusoidal Modulation and Empirical Mode Decomposition

A direct current (DC) Sagnac magnetic field sensor is a kind of fiber sensor based on alternate current magnetic field (ACMF) demodulation and empirical mode decomposition (EMD) to detect the magnetic field by measuring the phase variety caused by direct current magnetic field (DCMF). Commonly, Sagnac DCMF sensors can improve the magnetic detection sensitivity by using high Verdet constant (HVC) medium, which is expensive to prepare, or optical resonant cavity. However, the polarization diffraction in cavity restricts the performance of these devices. Meanwhile, none of them can suppress the electrical noise of the system such as 1/f noise. In this paper, we use ACMF modulation to couple the phase containing the DCMF information into the amplitude of the fundamental frequency component of the interference signal. Then we demodulate the signal by EMD to extract the fundamental frequency component. The designed sensor demonstrates a sensitivity of 4.651 mV/μT with an accuracy of 1.649 nT in the magnetic field range of 0-40 mT. It has the advantages of high stability, anti-electromagnetic interference and miniaturization.

Fine-grained transparent Dy2O3 ceramics fabricated from precipitated powders without sintering aids

As a promising material for Faraday isolator used in visible and infrared range, Dy2O3 ceramics with the average grain size of ∼800 nm and the in-line transmittance of 79.3% at 2000 nm and 70.0% at 633 nm were successfully fabricated. The Dy2O3 wet-chemically precipitated powders were densified in two steps consisting of vacuum pre-sintering and hot isostatic pressing (HIP) post-treatment. The precipitated precursor was calcined at 1150–1250 °C for 4 h in air to obtain Dy2O3 powders. The influences of calcination temperature on the morphology and sintering behavior of Dy2O3 powders were studied. The optical quality and microstructure of Dy2O3 ceramics with different pre-sintering temperatures were investigated. The Verdet constant of Dy2O3 ceramics at 633 nm is −322.1 ± 3.5 rad T−1 m−1, about 2.4 times that of commercial Tb3Ga5O12 crystals. Transparent Dy2O3 ceramics with high Verdet constant and suitable transparent windows present a prospective application for Faraday rotators.

Fabrication and performance optimization of novel (Tb0.9975R0.0025)3Sc2Al3O12 (R= Pr, Ho, Dy, Eu) magneto-optical transparent ceramics

Magneto-optical materials with high Verdet constants at high extinction ratios are desirable for the Faraday isolators. However, current terbium-based crystals have encountered several issues, such as low Verdet constants (TGG crystals), difficult growth (TSAG crystals), and low utilization of raw materials, which limit the development of the Faraday isolators. Here, R0.0025TSAG (R= Pr, Ho, Dy, Eu) transparent ceramics are prepared. The ceramics exhibit high optical transparency above 74.0% in the 525–1565 nm range and a high relative density of 98.9%. In particular, the transmittance of R0.0025TSAG ceramics at 1064 nm is approximately 81.6%, 81.6%, 79.8%, and 80.6%, respectively. The Verdet constants of R0.0025TSAG ceramics at the measurement wavelength are greater than those of the TSAG ceramic. The compelling magneto-optical performance of the Dy0.0025TSAG ceramic includes a high Verdet constant of 161.8 ± 3 rad·m−1·T−1 at 635 nm. The Verdet constant of the Dy0.0025TSAG ceramic is still superior to that of TSAG ceramic in the same temperature range. The extinction ratios of the R0.0025TSAG (R= Pr, Ho, Dy) ceramics exceed 40 dB. The figure of merit points out the superior characteristics of R0.0025TSAG ceramics. Moreover, R0.0025TSAG (R= Pr, Ho, Dy) ceramics with a thickness above the centimeter level are successfully prepared. This work indicates that the Dy0.0025TSAG ceramic can promote the miniaturization of magneto-optical isolators and can be applied in high-power lasers.

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 erbium concentration on the Verdet constant dispersion of LiY1.0-xErxF4 single crystal

The dispersion of the Verdet constant of LiY1.0-xErxF4 crystals was evaluated from 190 nm to 500 nm for different doping concentrations of Er ions. A 15% doping concentration yielded a high Verdet constant of 54.5 rad/(T·m) at 193 nm. This value can be explained by the contribution of the diamagnetic term associated with LiYF4 and the paramagnetic term of the Er ions. Although the LiYF4 crystal yielded a lower value of −36.6 rad/(T·m) at 193 nm from Er-doped LiYF4, it can be used in the vacuum–ultraviolet region because of its high transmittance at wavelengths longer than 120 nm.

Microstructure and Faraday effect of Tb2O3‐Al2O3‐SiO2‐B2O3 glasses for fiber‐based magneto‐optical applications

AbstractFor the fiber‐based magneto‐optical (MO) devices, like Faraday optical isolator, the target MO glasses are supposed to strike a balance among the following properties: high Verdet constant, chemical and physical stabilities, compatibility with the fiber drawing process, and the connectivity to the silica glass fiber networks. In this work, we report on the MO application of Tb2O3‐Al2O3‐SiO2‐B2O3 (TASB) glasses as a derivative of the yttrium aluminum silicate (YAS) glass fiber systems which have been intensively studied for their huge potential in the context of all‐fiber lasers. We found that MO properties of the obtained TASB glasses vary systematically with the B2O3 contents. The effects of B2O3 on the local glass structures and the valence state of Tb ions were clarified via nuclear magnetic resonance, electron spin resonance, X‐ray photoemission spectroscopy, and Raman spectroscopy. B2O3 content in TASB glasses leads to a certain degree of depolymerization in glass network and most of Tb4+ ions from the raw material of Tb4O7 are reduced to Tb3+ ions even in air, resulting in an improved MO properties. Due to the relatively high Verdet constant (∼70 rad/T/m) and suitable rheology of the glass melt speculated from the thermal analysis, TASB glass system in this work is adaptable to stable fiber‐based Faraday effect devices.

Thermo-optical properties of cryogenically cooled (Tb[formula omitted]Y[formula omitted])[formula omitted]O[formula omitted] ceramics

Due to a high Verdet constant and paramagnetic properties, the ceramics based on terbium oxide is a promising candidate as a magneto-optical medium for developing cryogenic Faraday isolators. Cryogenic cooling suppresses thermal effects and leads to an increase in the maximum power of the laser radiation passing through the Faraday isolator at the same isolation ratio. We have measured the thermally-induced depolarization and the thermal lens within the 81–297 K temperature range and the linear absorption coefficient α0 within the 83–297 K temperature range in (Tb0.9Y0.1)2O3. The ratio of the effective thermo-optical constants Peff/Qeff was ∼6.44 in the studied temperature region. On cooling to LN2 temperature, the parameters α0Qeff/κ and α0Peff/κ (κ is the thermal conductivity coefficient) decreased by a factor of ∼5.2. The α0 was temperature independent. The results of the study demonstrate great prospects for the use of terbium oxide based ceramics in cryogenic Faraday isolators.

Transparent non-stoichiometric Tb2.45Hf2O7.68 magneto-optical ceramics with high Verdet constant

Transparent Tb2.45Hf2O7.68 ceramics were fabricated successfully by reactive sintering at 1700 °C for 3 h with hot isostatic pressing (HIP) post-treatment at 1700 °C for 3 h. In-line transmittance of the Tb2.45Hf2O7.68 ceramic specimen with the thickness of 2.0 mm reached 79.4% at 1064 nm. X-ray diffraction was used to verify the existence of pyrochlore phase and the occupation sites of Tb3+ were discussed. Elemental mapping showed no secondary phase in Tb2.45Hf2O7.68 ceramics. Verdet constant of the Tb2.45Hf2O7.68 ceramics at 633 nm is -165.6 rad•T−1•m−1, which is 23.6% higher than that of commercial Tb3Ga5O12 crystal (-134 rad•T−1•m−1) and 8.4% higher than that of Tb2Hf2O7 (-152.8 rad•T−1•m−1). Tb2.45Hf2O7.68 ceramics with high Verdet constant are promising to be used in compact Faraday rotators.

Optical nonlinear, EPR, second harmonic generation and Faraday rotation studies on diamagnetic solid: Influence of thermal poling

The electric field manipulation of magnetic and magneto optical properties is currently of great interest for photonics and spintronics devices. In this study, for the first time, we utilized the thermal poling electric field induced polarization and magnetization to manipulate the magnetic and Faraday rotation performance of heavy metal oxide diamagnetic glass. The influence of poling conditions on second & third nonlinearity, structure and defects, thermal, magnetic and magneto optical properties were studied through varies characterization techniques such as scanning electron microscope, X-ray powder diffraction, Raman, maker fringe, electron paramagnetic resonance, X-ray photoelectron spectroscopy, Z-scan, vibration sample magnetometer and Faraday rotation measurements. 5 µm-thickness layer second harmonic generation intensity increased with the voltages from 1 kV to 3 kV, while at 300°C second harmonic generation the intensity decreased. Third nonlinearity coefficient and nonlinear refractive index were calculated to be much higher than that of un-poled glass through the Z-scan method. X-ray photoelectron spectroscopy, Raman and electron paramagnetic resonance analysis revealed the center-asymmetric network of glass, non-bridging oxygen and defect centers after thermal poling. The modification on glass structure resulted in the enhancement of magnetic moment of glass with electric induced magnetic field changes electric coupling effect as high as 15%. Faraday rotation measurement indicated that polarization dominantly contributed to the enhancement of V, at the same time, the V also was impacted by glass transmittance and crystal scattering. The optimized thermal poling condition was determined to be 3 kVand 260°C for 4 hours, under which thermally poled glass presented the strong second harmonic generation intensity (2.3 pm/V), highest Verdet constant (0.2382 min/G.cm) and improved diamagnetic susceptibility (0.424×10−5 emu/mol). Diamagnetic glass with these properties is attractive for magneto optical sensing and nonlinear applications.

Numerical analysis of magnetic field measurement based on Faraday rotation in a no-core tellurite fiber

In this work, a magnetic field measurement sensor based on Faraday rotation effect in TeO2-Li2O-WO3-MoO3-Nb2O5 no-core fiber (TLWMN NCF) is theoretically proposed. Compared with traditional silica fibers, TLWMN NCF has a higher Verdet constant, which makes contributions to improving the sensitivity. Comparative analysis concerning the Verdet constant and sensitivity of the designed sensor and its silica counterpart at different wavelength is presented, where the highest sensitivity of TLWMN NCF at measuring a uniform magnetic field can reach 2.2 × 10−3 rad/Gs at the wavelength of 442 nm, and the value decreases slightly when measuring a non-uniform magnetic field, which is 1.91 × 10−3 rad/Gs. The superior sensitivity and independence of other magnetic sensitive materials attribute the designed sensor an appropriate candidate in terms of magnetic field measurement in numerous fields.

Verdet constant of various types of honey and sugar solution analyzed at different concentration

The optical activity effect of material on the polarization of a light beam due to the external magnetic field has observed through Faraday rotation. The use of the Verdet constant represents the behaviour characteristic of the material. This paper had reported the Verdet constant of some honey types compared with a sugar solution that was analyzed at different concentrations. Laser He-Ne had been used to observe the change of its polarization angle (Faraday rotation) when the external magnetic field applied at 50 gauss, 100 gauss, and 150 gauss. They were produced by a solenoid wrapped around the sample container, connected to the DC power supply. The Verdet constants of Kaliandra honey, Randhu honey, and Pahit honey, respectively, indicate their dependence on concentration. The profile of concentration dependence of the Verdet constant for all three types of honey is the same as that of the sugar solution. However, the highest Verdet constant is achieved by Kaliandra honey when analysed at a concentration of 30%.

Magneto-optical glass mixed with Tb3+ ions: High Verdet constant and luminescence properties

Compared with crystal and transparent ceramics, magneto-optical glass is an attractive choice for applications in communication and larger power laser systems. However, the presence of rare-earth ions in magneto-optical glass can cause devitrification of the glass and require a higher melting temperature. This study aims to address these issues. High-temperature melting quenching technology was used to prepare highly transparent Tb3+ ion-doped GeO2-PbO-B2O3–SiO2 (GPBS) magneto-optical glass. Through XRD, FT-IR, DSC, chemical corrosion resistance, density test, UV–vis, fluorescence test, and Faraday rotation test, the effects of different Tb3+ ion concentrations on the thermal performance, chemical stability, structure, luminescence performance and magneto-optical performance of heavy metal oxide magneto-optic glass were studied. Notably, these glass materials exhibit high density, refractive index, optical basicity value, good thermal properties (101 °C), strong water and alkali resistance, excellent Faraday effect. The Verdet constants at different wavelengths also had notably high values. It was found that such glass has a strong green light emission at 544 nm, which demonstrates that this type of magneto-optical glass has broader application prospects in the preparation of laser elements and optoelectronic functional devices.

Bi1.9Mn0.1Te3 nanocrystal functionalized diamagnetic glasses: optical, luminescence, magnetic and Faraday rotation

Mn doped Bi2Te3 nanocrystal, both as topological insulator and diluted magnetic semiconductor, has gained significant interest due to its interesting magnetic performance roused by the sp-d exchange interaction and unique time-reversal symmetry protected surface states. In this paper, for the first time, Bi1.9Mn0.1Te3 nanocrystal doped diamagnetic TeO2–PbO–B2O3 glass was studied. Pure 50nm hexagonal Bi1.9Mn0.1Te3 nanocrystals were synthesized with a specific surface area of 64.28 m2/g using the optimized PEG as surfactant. Due to the complex spin-orbit interactions between sp band of Bi2Te3 and d band of Mn, the prepared Bi1.9Mn0.1Te3 displayed characteristic luminescence, A11g, E2g, A21g Raman modes, good photocatalytic (70.2%) and ferromagnetic/paramagnetic co-existence behavior.Bi1.9Mn0.1Te3 doped diamagnetic glasses were prepared by melting-quenching technique and the influence of different doping amount to glass structure and properties was evaluated through X-ray diffraction, Fourier transforms infrared, Raman, Ultraviolet-visible, photoluminescence spectra and Verdet constant measurement. The glasses structure and properties were doping amount dependent. X-ray diffraction, Fourier transforms infrared and Raman spectra revealed the evolution of structure units of TeO4, TeO3, BO3 etc under the modification of Bi1.9Mn0.1Te3. SEM revealed the homogeneity and growth of nanocrystals in matrix. X-ray photoelectron spectroscopy displayed the chemical states changes of Mn2p, Bi4f, Te3d and O1s under different doping amounts. Both the optical absorption band at 540nm and cutoff wavelength increased with the dopant amount. The luminescence in visible range revealed the tetrahedral coordination state of paramagnetic Mn ions which also influenced the magnetization and Faraday rotation accordingly. Experimental results showed that glass with 2%Bi1.9Mn0.1Te3 exhibited good optical, luminescence, magnetic, significant high Verdet constant (0.2522min/G.cm) and good thermal stability as well. Such good quality diamagnetic glass is attractive for magneto-optical devices applications in isolator and current transducer etc.

Study of the Verdet constant of the holmium-doped silica fiber

A Ho-doped silica fiber with a high verdet constant is prepared by a modified chemical vapor deposition (MCVD) method. The phenomenon of the Faraday effect enhancement of a Ho-doped silica fiber is theoretically analyzed by the wave transition contribution analysis method based on the wave-particle duality of light. The Verdet constant of Ho-doped silica fiber is calculated with the wavelength range from 1310 nm to 1550 nm. Through experimental measurement, it is found that the Verdet constant of the Ho-doped silica fiber has a wavelength dependency. The experimental results show that the Verdet constant values of the Ho-doped silica fiber at 1310 nm and 1550 nm are 4.5 times and 1.6 times that of the conventional single-mode silica fiber, respectively.

Crystal growth, thermal and optical properties of TSLAG magneto-optical crystals

Tb3Sc1.95Lu0.05Al3O12 (TSLAG) magneto-optical crystal, with higher Verdet constant and lower absorption coefficient, is a potential candidate to substitute the commercial TGG crystals. In this work, bulk TSLAG crystals with maximum dimensions of Ø 35 × 60 mm3 have been successfully grown by the Czochralski (Cz) method with a 60 mm diameter crucible. The effective segregation coefficient of Tb3+, Sc3+, Lu3+, Al3+ ions were 0.99, 0.87, 0.99 and 1.09, respectively. The use of pure starting materials and lower thermal gradients during growth led to significantly improved crystal properties such as the optical transmission characteristics at 1064 nm. Also the thermal properties have been investigated in detail, providing primary reference data for applications in the field of intense lasers.

Design and magneto‐optical characteristics of Ge–Sb–S–PbI2 chalcogenide glasses with a high Verdet constant

AbstractTo develop high‐performance magneto‐optical chalcogenide glasses and clarify the mechanisms of the Verdet constant, a series of GeS2–Sb2S3–PbI2 chalcogenide glasses were designed and fabricated, and their Faraday effects were investigated at a wavelength of 980 nm. A new parameter, that is, average polarizability, was proposed, and the results show that the Verdet constant has a good linear relationship with average polarizability, meaning that the Verdet constant of a chalcogenide glass can be directly estimated by its chemical constituents. The Verdet constant is as large as 0.200 min G−1 cm−1 at 980 nm for 22.5GeS2–67.5Sb2S3–10PbI2 composition glass, which is the largest value reported thus far for sulfide glasses; this glass also possesses good thermal and optical properties and therefore might be an attractive candidate for mid‐infrared magneto‐optical device applications.