Verdet Constant Research Articles

Fabrication and properties of transparent Tb2Ti2O7 magneto-optical ceramics

Transparent Tb2Ti2O7 magneto-optical ceramics were fabricated from co-precipitated nano-powders by vacuum pre-sintering with hot isostatic pressing (HIP) post-treatment. The formation of pyrochlore phase, decomposition of the precursor, and the morphology of powders calcined at different temperatures were investigated. The in-line transmittance of Tb2Ti2O7 ceramics, which were pre-sintered at 1350 ℃ for 2 h with HIP post-treatment at 1450 ℃ for 3 h and subsequently annealed at 800 ℃ for 20 h in NH3 atmosphere, reaches 65.5 % at 1064 nm. The Verdet constant of Tb2Ti2O7 ceramics is −229.0 ± 0.6 rad·T−1 m−1 at the wavelength of 633 nm, which is 71 % higher than that of the commercial Tb3Ga5O12 crystals. Tb2Ti2O7 magneto-optical ceramics show a promising application for Faraday rotators.

Thermo-Optical Studies of Laser Ceramics.

A cycle of works on manufacturing and studying laser and magnetooptical ceramics with a focus on their thermo-optical characteristics performed by the research team is analyzed. Original results that have not been published before such as measurements of the Verdet constant in the Zr:TAG, Re:MgAl2O4, and ZnAl2O4 ceramics are also presented.

Terahertz magneto-optical response of bismuth-gadolinium-substituted rare-earth garnet film.

We report the magneto-optical Faraday response of bismuth-gadolinium-substituted rare-earth iron garnet at terahertz frequencies ranging from 100 GHz to 1.2 THz. The maximum transmittance of ±45° component is about 60% near the frequency point of 0.63 THz. When the external magnetic field change from -100 mT to +100 mT, the Faraday rotation angle is between -6° and +7.5°. The overall change of ellipticity is relatively small. The maximum value of the Verdet constant is about 260 °/mm/T at 0.1 THz and then gradually decreases to 80 °/mm/T at 1.2 THz. Within the considered frequency range, the thick film exhibits magnetically tunable, non-reciprocal characters and a strong magneto-optical effect within a small external magnetic field at room temperature, which will be widely used for the terahertz isolators, circulators, nonreciprocal phase shifters, and magneto-optical modulators.

Introduction and measurement of the effective Verdet constant of spun optical fibers.

We introduce the term effective Verdet constant to describe the effect of spun fiber fabrication parameters on the Faraday polarization rotation sensitivity in response to a longitudinal magnetic field along the fiber. We obtain the expression of the effective Verdet constant of a spun fiber showing that it is always less than that of an ideal fiber free of birefringence by a factor relating to the ratio of spin twist rate to unspun fiber retardation per unit length. The larger the ratio, the closer the effective Verdet constant to that of the ideal fiber is. By measuring the polarization rotation in spun fibers with a highly accurate polarization analysis system made with binary polarization rotators, we experimentally obtain the effective Verdet constants of three different high birefringence spun fibers from three different manufactures at 1310 nm, with values of 1.07 × 10-6 rad/A, 1.05 × 10-6 rad/A, and 1.04 × 10-6 rad/A, respectively, which are 98%, 96%, and 95% of that of the ideal fused silica fiber free of birefringence. Our work is important for understanding the Faraday Effect in the spun optical fibers, as well as for quantifying the Faraday sensitivity of different spun fibers for electrical current and magnetic field sensing applications.

Highly Dy2O3 and Er2O3 doped boron-aluminosilicate glasses for magneto-optical devices operating at 2 µm

Magneto-optical glass materials with large Verdet constants at 2 μm have attracted increasing attention due to the significant advances of novel lasers operating at this wavelength region. In this paper, 13Al2O3-21B2O3-35.4SiO2-(30.6-X)Er2O3-XDy2O3 glasses have been synthesized, and their physical, optical, and magneto-optical properties were studied for making Faraday devices at 2 μm. A Verdet constant of as high as −5.9 rad/(T*m) at 1950 nm was measured with a 13Al2O3-21B2O3-35.4SiO2-30.6Dy2O3 glass. The temperature difference between crystallization and glass transition of 150 °C and the synthesis temperature of below 1500 °С make this glass very promising for making magneto-optical devices for 2 μm applications.

Magneto-optical performances of novel neodymium-doped CeF3 crystal

The highly transparent neodymium-doped CeF3 (Nd:CeF3) single crystal with diameter of 20 mm × 35 mm was grown by the Bridgman Stockbarger (BS) method. The optical and magneto-optical (MO) performances of Nd:CeF3 were experimentally investigated in UV–Vis and near-IR spectral range. Notably, Nd:CeF3 exhibits high transparency and significantly enhanced Faraday rotation. Compared with commercial terbium gallium garnet (TGG), Nd:CeF3 has higher Verdet constants at different measured wavelengths. The bulk laser-induced damage of c-cut Nd:CeF3 crystal was also determined by R-on-1 method. All the results demonstrate that the properties of Nd:CeF3 are superior to those of CeF3 and TGG. The excellent MO properties of Nd:CeF3 with a used wavelength of 0.3–2.2 µm are especially important for high power isolators in order to cover UV–Vis and the entire near-IR range.

C-Term Faraday Rotation in Metallocene Containing Thin Films.

The Faraday effect is a magneto-optical (MO) phenomenon that causes the plane of linearly polarized light to rotate when passing through a medium subjected to a parallel magnetic field. Informed by the established quantum mechanical model developed by Buckingham and Stephens, we sought to identify molecules that would exhibit large MO responses. Magnetic circular dichroism studies of ferrocenium in the 1970s revealed its potential as an MO material; however, it has not been evaluated in the context of Faraday rotation and thin-film optical applications. Herein, we report near-infrared (NIR) Faraday rotation in thin films of decamethylferrocenium/poly(methyl methacrylate) composites with maximum Verdet constants of -3.45 × 104 deg T-1 m-1 at 810 nm (absorbance = 0.09) and -1.44 × 104 deg T-1 m-1 at 870 nm (absorbance = 0.01). These polymer-metallocene thin films deliver larger Verdet constants than commercially used NIR inorganic Faraday rotators and are facile and inexpensive to produce. The temperature dependence and distinct lineshape of the MO responses observed in decamethylferrocenium radical cations, decamethylmanganocene, and chromocene are in accordance with the quantum mechanical model. The observation of a strong C-term Faraday rotation in solid-state organometallic materials provides the groundwork for the development of high-performance metallocene-based Faraday rotators.

Magneto-optical effects in a high-Q whispering-gallery-mode resonator with a large Verdet constant.

We have studied magneto-optical effects in an optical whispering-gallery-mode resonator (WGMR) manufactured from a Faraday-rotator material with, to the best of our knowledge, the record quality factor ($Q = 1.45 \times {10^8}$) achieved for such materials. We have experimentally measured the eigenfrequencies' deviation amplitude under the application of an external magnetic field and demonstrated the polarization plane declination over the light path. An analytical model for arbitrary magnetic field geometries in magneto-optic birefringent WRMRs has been developed.

Magneto-optical borogermanate glasses and fibers containing Tb3+

New glass compositions containing high concentrations of Tb3+ ions were developed aiming at the production of magneto-optical (MO) fibers. This work reports on the structural and MO properties of a new glass composition based on (100 − x)(41GeO2–25B2O3–4Al2O3–10Na2O–20BaO) − xTb4O7. Morphological analysis (HR-TEM) of the sample with the highest concentration of Tb3+ ions confirmed the homogeneous distribution of Tb3+ ions and the absence of nanoclusters. All the samples presented excellent thermal stability against crystallization (ΔT > 100 °C). An optical fiber was manufactured by a fiber drawing process. The UV–Vis spectra of the glasses showed Tb3+ electronic transitions and optical windows varying from 0.4 to 1.6 μm. The magneto-optical properties and the paramagnetic behaviors of the glasses were investigated using Faraday rotation experiments. The Verdet constant (VB) values were calculated at 500, 650, 880, 1050, 1330, and 1550 nm. The maximum VB values obtained at 650 and 1550 nm for the glass with x = 18 mol% were -128 and − 17.6 rad T−1 m−1, respectively. The VB values at 500 and 1550 nm for the optical fiber containing 8 mol% of Tb4O7 were − 110.2 and − 9.5 rad T−1 m−1, respectively, while the optical loss at around 880 nm was 6.4 dB m−1.

Application of Magneto-optical Characteristic in Liquid: Verdet Constant as Quality Indicator of Repeatedly Cooking Oil

The Faraday Effect is a magnetooptical phenomenon in physics describing the interaction of light and magnetic fields in a medium. A parameter that indicates the interaction is the Verdet constant. In this research, Verdet constant was measured on cooking oil that has been used several times. Magneto-optical properties were measured using the polarimetry method, which uses a He-Ne Laser beam with a magnetic field treatment of 50 gauss, 80 gauss and 100 gauss. The samples analyzed were bulk and non-bulk cooking oil. Repeated use of cooking oil causes a change in the polarization axis of the polarized laser. This has an impact on the Verdet constant of the material. The difference in the Verdet constant shows that the Verdet constant can be used as an indicator of cooking oil that has been used up to three times.

Large Faraday Rotation in Optical-Quality Phthalocyanine and Porphyrin Thin Films.

The magneto-optical phenomenon known as Faraday rotation involves the rotation of plane-polarized light as it passes through an optical medium in the presence of an external magnetic field oriented parallel to the direction of light propagation. Faraday rotators find applications in optical isolators and magnetic-field imaging technologies. In recent years, organic thin films comprised of polymeric and small-molecule chromophores have demonstrated Verdet constants, which measure the magnitude of rotation at a given magnetic field strength and material thickness, that exceed those found in conventional inorganic crystals. We report herein the thin-film magnetic circular birefringence (MCB) spectra and maximum Verdet constants of several commercially available and newly synthesized phthalocyanine and porphyrin derivatives. Five of these species achieved maximum Verdet constant magnitudes greater than 105 deg T-1 m-1 at wavelengths between 530 and 800 nm. Notably, a newly reported zinc(II) phthalocyanine derivative (ZnPc-OT) reached a Verdet constant of -33 × 104 deg T-1 m-1 at 800 nm, which is among the largest reported for an organic material, especially for an optical-quality thin film. The MCB spectra are consistent with resonance-enhanced Faraday rotation in the region of the Q-band electronic transition common to porphyrin and phthalocyanine derivatives, and the Faraday A-term describes the electronic origin of the magneto-optical activity. Overall, we demonstrate that phthalocyanines and porphyrins are a class of rationally designed magneto-optical materials suitable for applications demanding large Verdet constants and high optical quality.

Fantastic valence impacts of Pr on microstructures and Faraday magneto-optical effects of transparent (Ho,Pr)2O3 ceramics

Polycrystalline magneto-optical (Ho1-xPrx)2O3 (x = 0.05‒0.2) ceramics were fabricated by vacuum sintering using layered rare-earth hydroxides as the precursors, among which the 5 at.% Pr doped specimen exhibits the highest in-line transmittance of ∼76.1 % at 700 nm (∼94.5 % of the theoretical value of defect-free Ho2O3 single crystal) and the largest Verdet constant of −82 ± 6 rad∙T−1 m−1 at 1064 nm (∼2.3 times that of the commercial Tb3Ga5O12 crystal and ∼1.8 times that of the pure Ho2O3 ceramic). More Pr addition not only leads to a higher thermal decomposition temperature for the precursor but also a decreasing particle size for the oxide. A 5 at.% Pr dopant in Ho2O3 matrix generally exists in the oxidation state of +3, while an increasing Pr concentration up to 10 at.% induces coexisting valences of +3 and +4. The grain growth was suppressed by the present Pr4+ based on interstitial mechanism. The substitution of Pr3+ for Ho3+ is helpful for the rising Verdet constant of the binary ceramic, but Pr4+ has little positive contribution to it.

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.

TGT growth and magneto-optical properties of PrF3 crystal

High quality PrF3 crystal was successfully grown by the temperature gradient technique (TGT). The magneto-optical properties of PrF3 crystal were systematically investigated in the UV-VIS-NIR region. The advantage of PrF3 over CeF3 and TGG is its transparency in deep-UV region down to 258 nm. The dispersions of Verdet constant of PrF3 and TGG crystals in VIS-NIR region are similar. The Verdet constant of PrF3 crystal can theoretically increase from 677.93 rad T−1•m−1 at 300 nm to 967.53 rad T−1•m−1 at 270 nm. The CeF3 and TGG crystals aren't transparent in this region. Therefore, PrF3 crystal is the promising candidate for use as a Faraday rotator for optical systems operating below 300 nm.

Fabrication and performance evaluation of novel transparent ceramics RE:Tb3Ga5O12 (RE = Pr, Tm, Dy) toward magneto-optical application

Transparent ceramics are at the heart of modern magneto-optical materials providing promising opportunities for Faraday isolators. 1.0 at% RE:Tb3Ga5O12 (rare earth (RE) = Pr, Tm, Dy) transparent ceramics were successfully prepared by air sintering and sequential HIP technique using the coprecipitated powders as the raw material. All the powders have shown to be a pure cubic terbium gallium garnet (TGG) phase and exhibit good dispersion. Additionally, a change could not be observed in particle shape with the different doped ions. After the two-step sintering, all the obtained ceramics have good optical quality, and the in-line transmittances at 1070 nm are higher than 80%. Moreover, no secondary phase can be detected from the microstructures. However, the pores which remain entrapped in the ceramics can be noted. The Verdet constant of ceramic samples is optimized by RE doping, and the Verdet constant at 632.8 nm is about −143 rad·T−1·m−1, which is about 5% higher than that of TGG ceramics. Finally, the thermo-optical properties of 1.0 at% RE:TGG transparent ceramics are compared. The annealed TGG ceramic showed the best thermo-optical properties, and the thermally induced depolarization of 1.0 at% Ce:TGG and 1.0 at% Tm:TGG was inferior to that of annealed TGG ceramic.

Wavelength dependence of the Verdet constant in synthetic quartz glass for deep-ultraviolet light sources

Deep-ultraviolet (DUV) light sources are critical owing to their high photon energies and small diffraction limits, and synthetic quartz glass (SQ) is suitable for the Faraday rotators of DUV light. The Verdet constant in SQ was evaluated within the wavelength range of 190–300 nm. In addition to a high Verdet constant over the DUV region, this material exhibits a high transmittance without transitional absorption bands. The Verdet constants were found to be 70.1 rad/(T·m) at 193 nm, which is the shortest observed wavelength for silica glass. SQ glass has excellent structural properties; thus, it is suitable as a DUV Faraday rotator for high-average-power optical isolators.

Mixed valence effects in TbVO4: Y nanocrystals and diamagnetic materials: Structure, optical linear & nonlinear, magnetic and Faraday rotation properties

Diamagnetic Y3+ ions doped magneto-optical TbVO4 nanocrystals were synthesized and characterized, the influence of mixed valence effect in TbVO4: Y to structure and properties of diamagnetic glasses/ceramic was studied. 80–100 nm spherical TbVO4 nanocrystals were hydrothermally synthesized. The doping of 30% and 40% Y3+ into TbVO4 increased the grain size to 120–150 nm and transformed pure zircon-type to a combination of zircon- scheelite type structure. EDX, Raman and infrared spectra revealed that the Y3+ occupied the site of Tb3+ with chemical formula of Tb0.7Y0.3VO4 and Tb0.6Y0.4VO4 respectively. More than 40% Y3+ could not be incorporated into TbVO4 lattice. Y doped TbVO4 nanocrystals presented two absorption peaks at 266 nm and 301 nm and one broad emission peak centered at 468 nm. A quenching of emission was observed for 40%Y doped TbVO4 due to the non-radiation energy transfer between Tb3+ and Y3+. Three nanocrystals displayed EPR resonance signal at g = 1.98 for V4+ ions due to the ion (oxygen) vacancies and structure deformation. VSM and XPS results indicated that the Y3+ doping changed paramagnetic to diamagnetic due to the increase concentration of diamagnetic Y3+, V5+ and Tb4+ ions. Three nanocrystals doped diamagnetic glass/ceramic presented different transparency, homogeneity and structures because of multivalence states of Tb and V in glasses/ceramic. Pure TbVO4 and TbVO4:30%Y doped glasses exhibited transition 7F0→5D2 of Tb3+ and 2B2 g→2B1 g of V4+ ions which resulted in the reduction of band gap energy and red-shifts of absorption edges. A quenching of 5D4→7F5–2 transition of Tb3+ was observed in Tb0.6Y0.4VO4 doped ceramic. Closed and open-aperture Z-scan showed an enhancement of nonlinearity due to the increase of polarizability. The mixed valence states of Tb and V yielded different magnetization and magneto optical rotation performances in glasses/ceramic. TbVO4:30%Y doped glass exhibited remarkable third nonlinear susceptibility (7.66 × 10−11 esu), magnetization and Verdet constant (0.2248 min/G.cm) at 633 nm.

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%.

Sintering parameter optimization of Tb3Al5O12 magneto‐optical ceramics by vacuum sintering and HIP post‐treatment

AbstractTransparent terbium aluminum garnet (TAG) ceramics were achieved by the vacuum sintering plus HIP post‐treating from the coprecipitated TAG nanoparticles. The influences of vacuum sintering temperature and sintering aid TEOS on the optical quality of the TAG ceramics were studied. The results show that with the increase of sintering temperature, the optical quality of TAG ceramics is improved gradually, and the in‐line transmittance of the TAG ceramics treated at 1720°C for 20 hours under vacuum and then HIP post‐treated at 1700°C for 3 hours under 200 MPa argon gas is 81.6% at 1064 nm. The sintering additive TEOS can improve the optical quality of TAG ceramics and inhibit the valence state change of Tb3+ ions to Tb4+ during the annealing process. The Verdet constant of the TAG ceramics at 632.8 nm is about −178 rad·T−1·m−1 at room temperature, which is 1.3 times that of the commercial TGG crystals (−134 rad·T−1·m−1).