Faraday Rotation Method Research Articles

Faraday rotation method improves the upper limit of the electron electric-dipole-moment sensitivity.

The electron electric-dipole-moment (eEDM) is a powerful tool for exploring new particles. The candidates for eEDM search are heavy atoms and their molecules, which are well known for the obvious relativistic effect. Lead atom is considered to be the most ideal relativistic atom [Park et al., Nat. Commun. 11(1), 815 (2020)]. PbH molecule is an important representative of the Pb compound and is considered a cold candidate molecule due to the high diagonal Franck-Condon factors. We systematically investigated the (eEDM) searches of PbH using a two-component approach. The parity- and time-reversal symmetry violation constants of ground and excited states, including internal effective electric field Eeff, electron-nucleon scalar-pseudoscalar interaction constant WP,T, and nuclear magnetic quadrupole moment, were obtained and compared to other molecules. In addition, we designed two experimental methods to measure the sensitivity of the eEDM, indicating that the Faraday rotation method could greatly improve its sensitivity.

Метод эффективных вычитаний: работа с данными Иркутского радара некогерентного рассеяния

For incoherent scatter measurements, the effective subtraction technique is to alternate the duration of amplitude-modulated signals between a pair of consequently radiated pulses. The resulting gain of spatial resolution enables us to steadily assess the electron density profile by the Faraday rotation method. The paper describes the electron density measurement technique, which involves analyzing narrow-band signals from Irkutsk Incoherent Scatter Radar, and proposes an automated method of determining the electron density for the problem in which the convolution of the radiated signal waveform with backscatter signal cannot be neglected. The inverse problem of electron density recovery is considered as a standard nonlinear optimization problem, which is solved using the algorithms for global and local optimization applied consequently. We compare the electron density profiles obtained by analyzing different pulse waveforms and from Irkutsk ionosonde data.

Effective subtraction technique: implementation for Irkutsk Incoherent Scatter Radar

For incoherent scatter measurements, the effective subtraction technique is to alternate the duration of amplitude-modulated signals between a pair of consequently radiated pulses. The resulting gain of spatial resolution enables us to steadily assess the electron density profile by the Faraday rotation method. The paper describes the electron density measurement technique, which involves analyzing narrow-band signals from Irkutsk Incoherent Scatter Radar, and proposes an automated method of determining the electron density for the problem in which the convolution of the radiated signal waveform with backscatter signal cannot be neglected. The inverse problem of electron density recovery is considered as a standard nonlinear optimization problem, which is solved using the algorithms for global and local optimization applied consequently. We compare the electron density profiles obtained by analyzing different pulse waveforms and from Irkutsk ionosonde data.

Suppressing the false magnetic field in beam-splitting Faraday rotation measurement.

In laser-plasma experiments, the beam-splitting Faraday rotation measurement is usually used for mapping the magnetic field. Due to the geometric characteristics of the beam-splitting configuration, the split beams are not always incident normally on the image plane, and their spots have different shapes and intensity distributions. Ignoring these issues will inevitably introduce errors in polarization calculation and then generate large false magnetic fields. We introduced the restoration method to recover the spots and suppress the false magnetic field. We applied this method to ZEMAX simulation data and Shenguang-II experimental data. Compared to the method of directly overlaying the spots, it can reduce the average false magnetic field by about 50%. And the false magnetic field at the edge of the spot is reduced by one order of magnitude. We can highly improve the accuracy of the magnetic field measurement with the Faraday rotation method.

A Martin-Puplett interferometer (MPI) optical polarimeter: Design and laboratory tests.

Spontaneous and external magnetic fields interacting with plasmas are essential in high-energy-density and magnetic confinement fusion physics. Measuring these magnetic fields, especially their topologies, is crucial. This paper develops a new type of optical polarimeter based on the Martin-Puplett interferometer (MPI), which can probe magnetic fields with the Faraday rotation method. We introduce the design and working principle of an MPI polarimeter. With the laboratory tests, we demonstrate the measurement process and compare the results with the measurement result of a Gauss meter. These very close results verify the polarization detection capability of the MPI polarimeter and show the potential for its application in magnetic field measurement.

Application of Gel Method Ba2TiSi2O8 Ferroelectric Thin Film in Contemporary Handicraft Three-Dimensional Fiber Art Works

The concept of “fiber art” not only expresses a kind of art but also reflects the course of this art—the evolution from a material to an art. It also reflects the characteristics of this art form—art produced by materials. This article aims to explore the application analysis of the gel method Ba2TiSi2O8 ferroelectric thin film in contemporary handicraft three-dimensional fiber art works. This article first discusses the influence of ferroelectric domains on ferroelectric thin films and concludes that domains are the basis of various physical properties and applications of ferroelectric materials. By changing the types and quantities of domains, the performance of ferroelectric materials can be controlled. Then the measurement principle of the ferromagnetic resonance line width in the ferroelectric thin film is proposed, and the Ba2TiSi2O8 ferroelectric thin film is prepared by the gel method. Then the ferromagnetism and temperature stability of the Ba2TiSi2O8 ferroelectric film are discussed, and the contemporary handicraft three-dimensional fiber art works are analyzed based on the ferroelectric film. The classical methods to detect ferromagnetic permeability tensors mainly include non-resonance method, Faraday rotation method, resonance method, resonance perturbation method, and so on. The experimental results in this paper show that the polarization strength of the flexible film at high temperature is slightly reduced. As the temperature increases, the flexible film still has a good hysteresis loop, and the saturation polarization strength does not change much. It shows that the Ba2TiSi2O8 structured flexible film has good temperature stability at about 80°C, and the contemporary handicraft three-dimensional fiber art work based on ferroelectric film not only has a good economic mechanism but also has its flexibility and beauty increased by 80%.

A simple setup for in situ alkali metal electronic spin polarimetry.

Faraday rotation is considered a gold standard measurement of the electronic spin polarization of an alkali metal vapor produced under optical pumping. However, during the production of large volumes of hyperpolarized xenon gas, transmission monitoring measurements, otherwise known as field cycling measurements, are generally employed to measure the spin polarization of alkali metal atoms in situ as this method is easier to implement than Faraday rotation on standard polarizer setups. Here, we present a simple, low-cost experimental setup to perform Faraday rotation measurements of the electronic spin polarization of alkali metal atoms that can be easily implemented on standard polarizer setups. We then compare Rb polarization measurements obtained with the Faraday rotation method to those obtained with the transmission monitoring method. To our knowledge, a direct comparison of these methods has never been made. Overall, we found good agreement between the two methods, but at low Rb density and high laser power, we found evidence of nonlinear magneto-optical effects that may prevent Faraday rotation from being used under these conditions.

A review of methods for mitigating ionospheric artifacts in differential SAR interferometry

Interferometric synthetic aperture radar (InSAR) has been widely used to measure ground displacements related to geophysical and anthropic activities over the past three decades. Satellite SAR systems use microwave signals that interact with the ionosphere when they travel through it during the imaging processes. In this context, ionospheric variations can significantly contaminate SAR imagery, which in turn affects spaceborne InSAR measurements. This bias also leads to a decrease in the coherence and accuracy of InSAR measurements, especially for the low-frequency SAR systems. In this paper, we give an overview of the latest methods for mitigating the ionospheric contributions in InSAR, including Faraday rotation method, azimuth shift method, and range split-spectrum method, and only focus on the single pair of InSAR interferograms. The current challenges and future perspectives are outlined at the end of this paper.

Magnetic Domain Control of ErFeO3 by Intense Terahertz Free Electron Laser Pulses

The control of magnetic domain in correlated spin systems by optical pulses has been gaining importance in spintronics and related fields. In particular, ultrafast control of magnetic domain is one of the top areas of interest. Herein we demonstrate the magnetic domain control in ErFeO3 single crystal, a weak ferromagnet, induced by high-intensity terahertz (THz) pulse excitation from a free-electron laser. THz pulses with a central frequency of 4 THz and pulse energy in the order of 10 mJ were used. The microscopic images of the magnetic domain inversion induced by the THz irradiation were recorded by the Faraday-rotation method using a He–Ne probe laser. The experimental results of the THz pulse irradiation at room temperature and at low temperature around the spin reorientation phase transition are presented. We show that the THz pulse excitation can expand the minor magnetic domain toward the direction of the THz beam spot. The magnetic domain inversion is caused by the combination of depinning of the magnetic domain due to local heating and the entropic force owing to the thermal gradient induced by THz irradiation.

Dual-channel Faraday rotation measurement for pulsed magnetic field.

The immunity and survivability in a strong electromagnetic environment make the Faraday Rotation (FR) method irreplaceable for measuring pulsed magnetic fields. We present a dual-channel FR method that achieves more stable and precise measurement and more applicable magnetic field types than the conventional FR method. By splitting the modulated light into two components, the ratio of the two components is transformed into a tangent function with two analyzers at a relative 45°. The use of terbium gallium garnet, which has a significant magneto-optical effect, as a magneto-optical medium enables higher sensitivity for measurement. We have successfully measured the variation in magnetic flux density of the capacitively driven pulsed magnetic field.

Design of magneto-optic characterization properties of vegetable oil using Faraday rotation method based on microcontroller

The research aimed to design and create Faraday’s rotation system as a tool to characterize the magneto-optic properties of vegetable oil. The measured magnitude were the intensity of light, the magnitude of the magnetic field, and the change in the rotation angle of polarization. Measurement of light intensity was carried out using BH1750 as a light sensor, magnetic field measurement was carried out using Gauss meter. Changes in the rotation angle of polarization were made by the stepper motor which drove the lens of the analyzer which had been geared. The light source used was an RGB laser with a power 300mW. Data were collected by the initial condition of the angle between polarizer and analyzer lens at 45°. It can be concluded that Faraday rotation experiment is affected by heat produced by the solenoid and olive oil has magneto-optic property.

Modified Faraday Rotation Method for Studying Cesium Atomic Lines in Strong Magnetic Fields

A modified Faraday rotation method is developed using a nanocell filled with cesium vapor. Formed atomic lines have a spectral width 1.5–2 times narrower than those obtained by the Faraday rotation method. In magnetic fields of B = 5000–7000 G, all the atomic transitions of the Cs D2 lines, formed in the spectra, are spectrally resolved and identified. In particular, transitions that are forbidden at B = 0 G have been investigated, however, at certain values of the magnetic field, there is a gigantic increase in their probabilities. It is shown that the modified Faraday rotation method is convenient and efficient for high-resolution spectroscopy for Cs atoms. There is а good agreement between the experimental results and calculated values. The practical applications are also noted.

Note: An approach to 1000 T using the electro-magnetic flux compression.

The maximum magnetic field obtained by the electro-magnetic flux compression technique was investigated with respect to the initial seed magnetic field. It was found that the reduction in the seed magnetic field from 3.8 T to 3.0 T led to a substantial increase in the final peak magnetic field. The optical Faraday rotation method with a minimal size probe evades disturbances from electromagnetic noise and shockwave effects to detect such final peak fields in a reduced space of an inner wall of the imploding liner. The Faraday rotation signal recorded the maximum magnetic field increased significantly to the highest magnetic field of 985 T approaching 1000 T, ever achieved by the electro-magnetic flux compression technique as an indoor experiment.

Optical measurements and analytical modeling of magnetic field generated in a dieletric target

Polarization rotation of a probe pulse by the target is observed with the Faraday rotation method in the interaction of an intense laser pulse with a solid target. The rotation of the polarization plane of the probe pulse may result from a combined action of fused silica and diffused electrons. After the irradiation of the main pulse, the rotation angle changed significantly and lasted ∼2 ps. These phenomena may imply a persistent magnetic field inside the target. An analytical model is developed to explain the experimental observation. The model indicates that a strong toroidal magnetic field is induced by an energetic electron beam. Meanwhile, an ionization channel is observed in the shadowgraph and extends at the speed of light after the irradiation of the main beam. The formation of this ionization channel is complex, and a simple explanation is given.

Bayesian Data Combination for the Estimation of Ionospheric Effects in SAR Interferograms

The ionospheric propagation path delay is a major error source in synthetic aperture radar (SAR) interferograms and, therefore, has to be estimated and corrected. Various methods can be used to extract different kinds of information about the ionosphere from SAR images, with different accuracies. This paper presents a general technique, based on a Bayesian inverse problem, that combines various information sources in order to increase the estimation accuracy, and thus the correction. A physically realistic fractal modeling of the ionosphere turbulence and a data-based estimation of the model parameters allow the avoidance of arbitrary filtering windows and coefficients. To test the technique, the differential ionospheric phase screen was estimated by combining the split-spectrum method with the azimuth mutual shifts between interferometric pair images. This combination is convenient since it can benefit from the strengths of both sources: range and azimuth variations from the split-spectrum method and small-scale azimuth variations from more sensitive azimuth shifts. Therefore, the two methods can recover the long and short wavelength components of the ionospheric phase screen, respectively. A theoretical comparison between the Faraday rotation method and the split-spectrum method is also reported. For the use in the combination, precedence was then given to the split-spectrum method because of the comparable precision level, lower susceptibility to biases, and wider applicability. Finally, Advanced Land Observing Satellite Phased Array type L-band SAR L-band images are used to show how the combined result is more accurate than that obtained with the simple split-spectrum method.

Thermoelastic-tunable magnetic response of BiFeO3thin film on colloidal photonic crystal substrate fabricated by pulsed laser deposition

Investigation of the thermoelastic-tunable magnetic response of polycrystalline bismuth ferrite thin film is herein reported. The polycrystalline bismuth ferrite thin films were grown by room-temperature pulsed laser deposition on the designed polymer colloidal photonic crystal substrates. The evolution of these films was assessed by X-ray diffraction testing and scanning electron microscopy images. The thermal-dependent magnetic measurements and magneto-optical properties were also investigated as a function of deposition substrate and target–substrate distances via the Faraday rotation method. Due to the large anisotropic thermal deformation of the polymer colloidal interface, the huge rotation downshift was observed versus a slight thermal change. Furthermore, we found that this returnable reduction had the same behavior during the heating and cooling processes. This reversible thermal property of the polymer colloidal crystal in combination with the magnetic response of the multiferroic compounds can possibly lead to innovations in sensors and switches based on thermomagneto-optical coupling and facilitate the nanoscale thermal characterization.

Terahertz Dynamics of a Topologically Protected State: Quantum Hall Effect Plateaus near the Cyclotron Resonance of a Two-Dimensional Electron Gas.

We measure the Hall conductivity of a two-dimensional electron gas formed at a GaAs/AlGaAs heterojunction in the terahertz regime close to the cyclotron resonance frequency using highly sensitive Faraday rotation measurements. The sample is electrically gated, allowing the electron density to be changed continuously by more than a factor of 3. We observe clear plateaulike and steplike features in the Faraday rotation angle vs electron density and magnetic field (Landau-level filling factor) even at fields or frequencies very close to cyclotron resonance absorption. These features are the high frequency manifestation of quantum Hall plateaus-a signature of topologically protected edge states. We observe both odd and even filling factor plateaus and explore the temperature dependence of these plateaus. Although dynamical scaling theory begins to break down in the frequency region of our measurements, we find good agreement with theory.

A sensitive Faraday rotation setup using triple modulation.

The utilization of polarized targets in scattering experiments has become a common practice in many major accelerator laboratories. Noble gases are especially suitable for such applications, since they can be easily hyper-polarized using spin exchange or metastable pumping techniques. Polarized helium-3 is a very popular target because it often serves as an effective polarized neutron due to its simple nuclear structure. A favorite cell material to generate and store polarized helium-3 is GE-180, a relatively dense aluminosilicate glass. In this paper, we present a Faraday rotation method, using a new triple modulation technique, where the measurement of the Verdet constants of SF57 flint glass, pyrex glass, and air was tested. The sensitivity obtained shows that this technique may be implemented in future cell wall characterization and thickness measurements. We also discuss the first ever extraction of the Verdet constant of GE-180 glass for four wavelength values of 632 nm, 773 nm, 1500 nm, and 1547 nm, whereupon the expected 1/λ(2) dependence was observed.

Magnetic Orders of Highly Frustrated Spinel, ZnCr2O4 in Magnetic Fields up to 400 T

We investigated the magnetization process of the highly frustrated spinel ZnCr2O4 using the Faraday rotation method at 6 K under the ultra-high magnetic fields up to 400 T by the electro-magnetic flux compression method. We successfully observed the full magnetization process in this material. We found some anomalies which show new phase transitions at 240 T, 290 T, 350 T, and 390 T.

Magnetization of highly frustrated Zn-chromium spinel oxides up to a megagauss magnetic field

Precise magnetization processes of ZnCr2O4 were obtained by means of the Faraday rotation method subjected to ultra high magnetic fields up to 190 T generated by a single turn coil technique. In magnetization processes of ZnCr2O4, there observed a coplanar 2:1:1 canted state (the cant 2:1:1 phase) which is predicted by the theoretical model including a spin-lattice coupling. A magnetic-field width of the 1/2 plateau widens as the temperature increases.