Faraday Cell Research Articles

Magneto-optical properties of borophosphate glasses co-doped with [formula omitted] and [formula omitted]ions

Glasses from lithium-aluminum-zinc-boron-phosphorous oxide system co-doped with terbium (Tb3+) and dysprosium (Dy3+) oxides were studied for magneto-optical applications in lasers. The Fourier Transform Infrared and Raman Spectroscopy complementary analysis suggested the depolymerization of the boro-phosphate glass network by adding and increasing the rare-earth (RE) oxide content. Main UV–vis absorption maxima of Tb and Dy ions were identified at 348 and 1266 nm. Spectroscopic ellipsometry indicated a maximum refractive index of 1.56, at 400 nm, for the highest RE content. The Verdet constant amplified by increasing the RE content, reaching for the 9 mol% RE co-doped sample a value of -0.075 min/Oe/cm at 630 nm. The Faraday rotation angle was additionally confirmed by using a Faraday Cell Device, being also related to the specific paramagnetic behavior evidenced by Superconducting Quantum Interference Device magnetometry. The magneto-optical properties recommend such vitreous co-doped materials for magneto-optical devices.

Model of the spectral dependence of changes in the polarization state of laser radiation in magneto-optical crystal in the presence of multiple reflections from its faces

In this work we investigated the phenomena in the Faraday rotator that can affect the polarization state of transmitting laser radiation. We have found that multiple reflections of radiation from the faces of the terbium gallium garnet (TGG) crystal can cause deterioration of radiation extinction ratio and, therefore, isolation properties of Faraday cell. We were able to calculate the impact of this factor on polarization extinction ratio of monochromatic and quasimonochromatic laser radiation transmitting through the crystal.

Coupling biomass pretreatment for enzymatic hydrolysis and direct biomass-to-electricity conversion with molybdovanadophosphoric heteropolyacids as anode electron transfer carriers

Molybdovanadophosphoric heteropolyacids have been employed as anode electron carriers for coupling pretreatment of wheat straw and direct conversion of the biomass to electricity, which can provide a new idea for lignocellulose conversion to energy. • Molybdovanadophosphoric heteropolyacids as anode electron transfer carriers. • Coupling biomass pretreatment and direct biomass-to-electricity conversion. • Cellulose enzymatic digestibility was well improved. • Electricity co-generation by re-oxidization of the electron carriers. • Pretreatment as the “charging” process. • Re-oxidation of electron carriers as the “discharging” process. Owing to their acidity, oxidizing ability and redox reversibility, molybdovanadophosphoric heteropolyacids (H n +3 PMo 12- n V n O 40 , abbreviated as PMo 12- n V n ) were employed as electron transfer carriers for coupling biomass pretreatment for enzymatic hydrolysis and direct biomass-to-electricity conversion. In this novel coupled process, PMo 12- n V n pretreatment that causes deconstruction of cell wall structure with PMo 12- n V n being simultaneously reduced can be considered as the “charging” process. The reduced PMo 12- n V n are further re-oxidized with release of electrons in a liquid flow fuel cell (LFFC) to generate electricity is the “discharging” process. Several Keggin-type PMo 12- n V n with different degree of vanadium substitution (DS V , namely n ) were prepared. Compared to Keggin-type phosphomolybdic acid (PMo 12 ), PMo 12- n V n ( n = 1–6) showed higher oxidizing ability but poorer redox reversibility. The cellulose enzymatic digestibility of PMo 12- n V n pretreated wheat straw generally decreased with increase in DS V , but xylan enzymatic digestibility generally increased with DS V . PMo 12 pretreatment of wheat straw at 120 °C obtained the highest enzymatic glucan conversion (EGC) reaching 95%, followed by PMo 11 V 1 pretreatment (85%). Discharging of the reduced heteropolyacids in LFFC showed that vanadium substitution could improve the maximum output power density ( P max ). The highest P max was obtained by PMo 9 V 3 (44.7 mW/cm 2 ) when FeCl 3 was used as a cathode electron carrier, while PMo 12 achieved the lowest P max (27.4 mW/cm 2 ). All the heteropolyacids showed good electrode Faraday efficiency (>95%) and cell discharging efficiency (>93%). The energy efficiency of the coupled process based on the heat values of the products and generated electric energy was in the range of 18%–25% depending on DS V . PMo 12 and PMo 11 V 1 seem to be the most suitable heteropolyacids to mediate the coupled process.

Model of the polarization extinction ratio change due to multiple reflection of laser radiation from the faces of the terbium-gallium garnet crystal in Faraday rotator

In this work we investigated the phenomena in the Faraday rotator, that can affect the polarization state of transmitting laser radiation. We considered two factors that can cause deterioration of radiation extinction ratio and, therefore, isolation properties of Faraday cell: multiple reflections of radiation from the faces of the TGG crystal and imperfection of the laser beam input relative to the central axis of the crystal. We were able to calculate the impact of these factors on polarization extinction ratio of laser radiation transmitting through the crystal.

Spectroscopic Detection of Magneto-Optical Hysteresis in a Single Magnetic Field Sweep by Faraday Cell Modulation

A rapid magneto-optical (MO) spectrometer is introduced. In conventional MO measurements, a monochromator produces quasimonochromatic incident light. The MO spectrum is then found by measuring the hysteresis loop at each wavelength in small steps, which is time consuming. In contrast, the new system uses 1) incident white light, 2) polarization rotation by a Faraday cell and spectroscopic detection using an area sensor, and 3) subtraction of spectra for small changes of polarization. By this method, an MO spectrum can be measured in only a few minutes with a single sweep of the magnetic field, enabling rapid exploration of the magnetic properties of a wide variety of materials.

A new conformal technique of inhomogeneous cells based on electric field strength weighted values

In this paper, a new method of using the electric field numerical weight to process the inhomogeneous cells is proposed, which is to resolve the problems such as high errors and parallel direction excluded in the existing finite-difference time-domain method. Instead of deriving average dielectric constant, the new method weights the electric field strength, which is the true solving variables, according to the mean value theorem, and then the length of the integral path is multiplied by the weight. In the new method both the discontinuous effects of inhomogeneous Ampere cell and the ones of inhomogeneous Faraday cell are taken into account, so it is accurate, easy to implement, versatile, and applicable to any of the various positional relationships between the dielectric interface and the electric field strength variable. A numerical model of dielectric filled circular waveguide is used for the numerical calculation and simulation, in which the deviations of the characteristic roots in two-dimensional TE mode solved by different methods from the theoretical ones are compared, and the anisotropies of different methods are also compared. The numerical result shows that the characteristic roots solved by the presented method are closer to the theoretical ones and the anisotropy caused by the proposing method is lower, which proves that this method is more efficient to process the inhomogeneous cells.

Bias characteristics of a multioscillator ring laser gyro with consideration of differential losses

Bias characteristics of the multioscillator ring laser gyro using Faraday cell (FLAG) have been investigated with both numerical simulation and experiment methods. We calculated the bias as a function of magnetic field strength and detuning for several FLAGs with different parameters. The results give some interesting findings. Firstly, the FLAG bias as a function of magnetic field strength and detuning have a cross point which corresponds to a feature bias if differential losses are not considered. It means that at the feature magnetic field strength, the bias of the FLAG is insensitive to the variation of detuning and at the feature detuning, the bias of the FLAG is insensitive to the variation of magnetic field strength. Secondly, differential direction loss and magnetic circular dichroism loss have influences on the feature magnetic field strength while differential polarization loss does not have. Experimental results verified the rule qualitatively and indicated the FLAG always had a feature detuning. The intrinsic bias characteristics are significant to the development of a high performance FLAG.

Finer Silver Nano-Particle Producing in Water Utilizing a Dielectric Bed

An fine silver particle has a variety of uses, such as in killing micrograms and as catalysts. Many techniques have been used for the production of the fine particles. Faraday cell, consisting of two silver electrodes in an electrolyte, is unique, but it is hard to get a very fine particle by this method. A finer silver nano-particle producing cell, utilizing a dielectric bed as a lower electric current and higher field controlling means, has been proposed and investigated. The I-V characteristics of the cell and effect of the dielectric bed on the producing finer silver nano-particles have been investigated. The I-V characteristics of the cell with the dielectric bed were different from that of the same system without the bed, due to the increased cell resistance and elevated electric field intensity. It is found that the proposed cell with the dielectric bed can produce finer silver nano-particles effectively, which, however, can be used as one of effective fine silver nano-particle producing means.

An optical polarization-bistable element based on the Faraday effect

An optical polarization-bistable element scheme based on an He-Ne laser (λ = 3.39 μm) with a Faraday cell in the cavity is considered for the first time. A sample of such cavity having the shape of a parallelepiped has been manufactured from an yttrium iron garnet single crystal and a theoretical analysis of this element in terms of the Jones matrices has been performed. It is established that the polarization bistability can be observed for a single-trip Faraday rotation of 45°. Experiments with the device based on a hybrid bistability scheme showed that, under certain conditions, the circular polarization is reversibly switched between σ+ and σ−.

Q & A EXPERIMENT TO SEARCH FOR VACUUM DICHROISM, PSEUDOSCALAR–PHOTON INTERACTION AND MILLICHARGED FERMIONS

A number of experiments are underway to detect vacuum birefringence and dichroism — PVLAS, Q & A, and BMV. Recently, PVLAS experiment has observed optical rotation in vacuum by a magnetic field (vacuum dichroism). Theoretical interpretations of this result include a possible pseudoscalar–photon interaction and the existence of millicharged fermions. Here, we report the progress and first results of Q & A (QED [quantum electrodynamics] and Axion) experiment proposed and started in 1994. We use a 3.5-m high-finesse (around 30,000) Fabry–Perot prototype detector extendable to 7-m with the cavity mirrors suspended using X-pendulum-double pendulums. To polarize the vacuum, we use a 2.3-T dipole permanent magnet rotated at 5–10 rev/s, with 27-mm-diameter clear borehole and 0.6-m field length. Our ellipsometer/polarization-rotation-detection-system is formed by a pair of Glan–Taylor type polarizing prisms with extinction ratio lower than 10-8 together with a polarization modulating Faraday Cell with/without a quarter wave plate. Our first results give (-0.2 ± 2.8) × 10-13 rad/pass with 18,700 passes through a 2.3 T 0.6 m long magnet for vacuum dichroism measurement. We present our experimental limit on pseudo-scalar-photon interaction and millicharged fermions.

Decay and fusion of polarization umbilics in a singular beam passed through a crystal

Evolution of polarized umbilics in a laser beam propagating in an optical system consisting of two anisotropic crystals with crossed optical axes and a Faraday cell is analyzed. It is shown that the phase perturbation caused by the second crystal results in radial shifts of the singularities, whereas the rotation of the plane of polarization when the Faraday cell is placed between the crystals causes angular displacements. When the Faraday cell is placed behind the second crystal, it provides additional fine control of the linear and angular shifts of the optical vortices.

Harmonic-based gain compensation method in optic sensors with separate light paths.

We describe a method for the compensation of gain unbalance in optical sensors with separate light path that involve two separate detection and conditioning electronic devices. The method is based on the digital measurement of harmonics of the output intensities from each path by means of the fast Fourier transform algorithm. The quotient of the amplitude of harmonics allows us to calculate the unbalance between paths and to compensate for it. In particular, this method can be applied electric power and current sensors that use Faraday and Pockels cells to measure current and voltage, respectively.

Observation of in plane magnetization reversal using polarization dependent magneto-optic Kerr effect

We present an experimental setup for in plane two axis magnetometry using the polarization dependent magneto–optic Kerr effect (MOKE). A conventional setup to measure longitudinal MOKE with crossed polarizers is extended by a Faraday cell to compensate for the rotation of the polarization vector caused by a magnetized sample. The shape of the hysteresis loops measured on thin FeNi alloy films depends strongly on the angle between the optical axis of the analyzer and the plane of incidence. We derive expressions for the compensation angle which allow for extraction of vectorial magnetic information from loops detected with oblique polarization. For a small deviation from pure s or p polarization the transverse magnetization is found to be proportional to the difference between the loop obtained with oblique polarization and the one obtained with pure s or p polarization. Thus the complete in plane reversal process split up into longitudinal and transverse components can be observed.

Optical electric-power-sensing system using Faraday and Pockels cells

We present what to our knowledge is a novel optical electric-power-sensing system that uses a cascade of a Faraday cell and a Pockels cell. According to Jones-matrix analysis, the electric-power information is contained in the intensity of the emerging light. An instantaneous ac electric-power signal has been observed in real time, and the active power has been measured in the 0-1-kW range. The experimental results are in good agreement with the theoretical analysis and prove the feasibility of the optical sensing system.

A very sensitive Faraday effect current sensor using a YIG/ring-coretransformer in a transverse configuration

A new and unusual type of Faraday cell/ring-core optical currenttransformer characterized by a transverse configuration of the light beamand current-induced magnetic field is developed. A fibre-linked current sensorsystem is constructed using a small bulkyttrium iron garnet as the Faraday cell. It is shown that the sensor has the highest ever reportedsensitivity of about 20% A-1 in modulation depth of the output light powerwith a very good linearity for currents below 1 A and has a very good isolationfrom surrounding currents.

Faraday compensator of reciprocal optical anisotropy utilizing a polarization ring interferometer

It is shown that a polarization ring interferometer containing a Faraday cell can be used to compensate the reciprocal anisotropy in round-trip optical circuits. It is established theoretically and experimentally that, unlike the case of conventional Faraday mirrors, the quality of the restoration of the polarization in a compensator based on a polarization ring interferometer is practically independent of the Faraday rotation angle. A deviation of the Faraday rotation angle from 45° leads only to an additional power loss. The novel compensators can be used in fiber-optic circuits with a wideband light source or with several sources having different wavelengths.

Fiber ring laser with flint glass fiber and its sensor applications

A new fiber ring laser has been proposed which is composed of a laser diode amplifier, a flint glass fiber as a sensing element, and a Faraday cell as a bias element, and applied to a frequency-domain sensor in which nonreciprocal effects such as current or rotation can be measured from a frequency change in the beat signal. A sign of current or rotation direction can be determined and a lock-in phenomenon is avoided owing to the bias element.

Single glass block faraday effect current sensor with homogeneous isotropic closed optical circuit

A new scheme is proposed for achieving a closed, homogeneous, and isotropic optical circuit necessary for high-accuracy optical-current sensors. It makes use of a single solid polygonal solid with reflection surfaces coated by quarter-wavelength dielectric thin-film layers for the Faraday cell. We derive the design principle and show numerically its applicability in various Faraday materials. The cross talk with the surrounding current is investigated in particular detail both theoretically and experimentally. In the example experiment with a SF57 Faraday material, a low cross talk is demonstrated for nearby currents.

Development of bulk-optic current sensor using glass ring type faraday cells

Bulk-optic current sensors have been developed for electric power systems. This current sensor has a glass ring type Faraday cell, where a light beam circulates around a current-carrying-conductor to precisely measure the current. Fundamental performances and practical applications are described.

Development of fault detector for 33‐kV ungrounded power line

AbstractA fault section detection system is being developed for 33‐kV ungrounded power line. The fault section is obtained from the relation of two point zero‐phase currents on power line. This fault detector is composed of optical current sensors and the processing unit and solar battery system. The optical current sensor consists of a Faraday cell and a porcelain bushing. Zero phase current on the processing unit is obtained through a three‐phase composer with auto gain control and residual current eliminator.This fault detector has the ability of 0.15 A zero‐phase current detection fault factory test; in field tests, this fault detector detects ground fault.