Large Faraday Rotation in Pyrolysis Synthesized Carbon Dots

There are several radio sources with Faraday rotation measures larger than 500 rad m−2 (ref. 1). Because most of these sources are located near the galactic plane, the large rotation measures can be attributed to the galactic medium2. However, a few sources at high galactic latitude also show large rotation, implying intrinsic Faraday rotation within the source. Until now, no sources have been discovered to have a rotation measure > 1,000 rad m−2. Using a multichannel polarimeter at 10 GHz attached to the 45-m radio telescope at Nobeyama, we have observed about 100 extragalactic radio sources which were suspected to have large rotation from our polarization catalogue1. Four of these 100 sources were found to have an intrinsic rotation measure > 1,000 rad m−2. Here we report rotation measures which are two orders of magnitude larger than those observed so far for most extragalactic radio sources. Two of these four sources are classified as compact steep-spectrum sources.

Summary form only given. In recent years, Inoue and Fujii have studied theoretically and experimentally, the one-dimensional magnetophotonic crystal (1-D MPC) multilayer films composed of magneto-optical and dielectric materials. This 1-D MPC film exhibits an extremely large magneto-optical Faraday rotation due to the weak localization of light Such 1-D MPC film offers the possibility of realizing a rotation of 45/spl deg/ with a thickness of only several microns. The application from showing high transmittance (T) and large Faraday rotation (/sup /spl Theta///sub F/) to a variety of magneto-optical devices for optical communication (ex. film-based optical isolator) is expected. Therefore, we investigated on the possibility of the application to optical isolator (T>95%, /sup /spl Theta///sub F/=45/spl deg/) for the optical communication of 1-D MPC from the theory.

Large Faraday rotations are reported tor Rh4+-substituted magnetic garnets in the visible wavelength region, in comparison with those observed in Ir4+ substituted ones. Although rather strong absorptions are observed in the visible region, no absorption peaks corresponding to the Faraday rotation peaks are observed in the absorption spectra. In order to study the origin of the Faraday rotations, Rh4+-and Ir4+-substituted nonmagnetic garnet films are prepared by an LPE method and optical absorption spectra are measured. In addition, the electronic state calculation of (M4+O62-)8- (M=Rh,Ir) octahedral clusters are performed by using the SCF-Unrestricted -SW Xα method. From the observed absorption spectra in nonmagnetic garnets and the electronic state calculations, large Faraday rotations are assigned to the charge transfer transitions of an electron from O 2p to Rh 4d or Ir 5d orbitals, or t1un → t2g* and t2un → t2g* transitions.

Faraday rotation, the rotation of the polarization of light due to a magnetic field in the direction of propagation of the light, is used in applications ranging from quantum memory to the detection of biomagnetic fields. For these applications large Faraday rotation is necessary, but absorption of light is detrimental. In search of these properties, we have characterized the Verdet constant of a so far unexplored class of mesogenic organic molecules. We report their spectra and provide an interpretation. A Verdet constant of almost 2.5 × 105 deg T–1 m–1 is found around 520 nm. This Verdet constant is 3 orders of magnitude larger than the largest known for organic molecules in a region without spectral features. We attribute this enormous Faraday rotation to resonant enhancement by a triplet excitation that does not appear in the linear absorption spectrum and to near-resonant enhancement by low-energy singlet excitations. Furthermore we are able to switch the Faraday rotation by changing the liquid cryst...

Advances in fibre Bragg grating technology for magnetic field sensing: A review

One of the best magneto‐optical claddings for optical isolators in photonic integrated circuits is sputter deposited cerium‐doped terbium iron garnet (Ce:TbIG) which has a large Faraday rotation (≈−3500° cm−1 at 1550 nm). Near‐ideal stoichiometry of Ce0.5Tb2.5Fe4.75O12 is found to have a 44 nm magnetic dead layer that can impede the interaction of propagating modes with garnet claddings. The effective anisotropy of Ce:TbIG on Si is also important, but calculations using bulk thermal mismatch overestimate the effective anisotropy. Here, X‐ray diffraction measurements yield highly accurate measurements of strain that show anisotropy favors an in‐plane magnetization in agreement with the positive magnetostriction of Ce:TbIG. Upon doping TbIG with Ce, a slight decrease in compensation temperature occurs which points to preferential rare‐earth occupation in dodecahedral sites and an absence of cation redistribution between different lattice sites. The high Faraday rotation, large remanent ratio, large coercivity, and preferential in‐plane magnetization enable Ce:TbIG to be an in‐plane latched garnet, immune to stray fields with magnetization collinear to direction of light propagation.

In this paper, a 4×4 transfer matrix method has been used to investigate the optical and magneto-optical properties of 1D conjugated photonic crystal (CPC) heterojunctions containing plasma layers. A linearly polarized TM wave is obliquely incident onto stack. A large Faraday rotation as well as high transmission can be achieved simultaneously in our proposed structure. The influences of the external magnetic field, number of unit cells, incidence angle, and plasma frequency on the transmission and Faraday rotation angle have been analyzed. Results indicate that the proposed structure has strong enhancement of Faraday rotation angle with relatively high transmission. This prospective advantage of the structure is useful for tunable filters in the millimeter-wave region.

Magnetized plasmas traversed by linearly polarized light will reveal their presence by the frequency dependent Faraday rotation of the angle of polarization. The regions surrounding the black holes powering the jets in AGNs are expected to have dense magnetized plasmas, possibly giving rise to very large Faraday rotations. Compact steep spectrum (CSS) sources are good candidates to search for very large Faraday rotated components as they contain compact emission from close to the black hole and many are strongly depolarized at centimeter wavelengths as expected from strong Faraday effects. We present data on several CSS sources (3C 48, 3C 138, and 3C 147) observed with the VLA at frequencies between 20 and 48 GHz in the most extended configuration. Large, but not excessive rotation measures are reported. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Bi2.5Y0.5Fe5O12 and Bi3Fe5O12 thin films were prepared on Gd3Ga5O12 substrates using a metal organic decomposition (MOD) method as magneto-optical indicators (MOI) to visualize the distribution of magnetic flux. Their structural and magneto-optical properties were studied. The Faraday rotations of Bi2.5Y0.5Fe5O12 and Bi3Fe5O12 thin films were 15.5 μm/degrees at a wavelength of 524 nm for the former and 23.0 μm/degrees at 530 nm for the latter. We found that these films prepared by MOD were suitable for MOI, because of their large Faraday rotation, in-plane magnetic anisotropy, and extinct magnetic domain structures.

Verdet constant is one of the key parameters to characterize the material's magneto-optical properties, along with the wavelength and temperature dependence. In order to thoroughly analyze the influence mechanisms of the incident wavelength and temperature on the Verdet constant as well as uncover its essence, both advantages and disadvantages of the classical electronic dynamics theory and quantum theory on account of basic theories and test data are discussed. By exploring the physical essences and models of the two theories, their significant associations between the medium's polarization intensity and the molecular polarizability are determined. The former decides the medium's permittivity and refractivity, and in turn, influences the Faraday rotation angle and Verdet constant. It should be noted that the polarizability includes not only those transition dipole moments from the electrons' transitions between different states, but also the inductive dipole moments which is due to the non-transition electron cloud being polarized. Hence, a hypothesis is proposed which suggests that the Faraday effect results from the combination of various factors. Accordingly, a theory of wave-transition contribution to the Verdet constant is deduced. Taking the typical diamagnetic material ZF1 and the typical paramagnetic material TGG as examples, the influences of the incident wavelength and the temperature on the Verdet constant are analyzed. The deduced theory together with the corresponding models is tested and verified by analyzing the relevant parameters and the test data. The results show that the wave-transition contribution theory and its models are superior in the aspect of precisely describing the material's Verdet constant.

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.

采用高温熔融法制备了高Tb3＋离子含量的GeO2-B2O3-SiO2系统磁光玻璃,测试了其Verdet常数和发光性能,探究了玻璃的Faraday效应、发光性能及光学碱度。研究结果表明：Verdet常数和光学碱度均随着Tb2O3含量的增加而线性增大,当Tb2O3摩尔分数为70%时,Verdet常数达到-5 000 min·T^-1·cm^-1（632.8nm）,所有磁光玻璃样品随Tb2O3含量变化均发出明亮的黄绿光。由于浓度猝灭效应,高Tb2O3含量缩短了Tb^3＋离子间距,增强了交叉弛豫效应,降低了发光强度和荧光寿命。

To 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.

Bi 3+ -substituted composite rare-earth iron net (TbYbBiIG) bulk single crystals were successfully grown by the flux method. The Faraday rotation F = 100 to 200 degree/mm and the optical transmission spectrum were measured in the near-infrared wavelength range of 1.0 to 1.7 μm. The temperature coefficient of Faraday rotation d F /dT = 2.0 × 10 2 degree mm -1 K 1 at wavelength λ = 1.55 μm in the temperature range of 273 to 360 K. It shows that the new type TbYbBiIG bulk single crystals have not only larger Faraday rotation F but also smaller d F /dT value than those of other rare-earth iron garnets.

Materials with magneto-optic (MO) properties have enabled critical fiber-optic applications and highly sensitive magnetic field sensors. While traditional MO materials are inorganic in nature, new generations of MO materials based on organic semiconducting polymers could allow increased versatility for device architectures, manufacturing options, and flexible mechanics. However, the origin of MO activity in semiconducting polymers is far from understood. In this paper, we report high MO activity observed in a chiral helical poly-3-(alkylsulfone)thiophene (P3AST), which confirms a new design for the creation of a giant Faraday effect with Verdet constants up to (7.63 ± 0.78) × 104 deg T-1 m-1 at 532 nm. We have determined that the sign of the Verdet constant and its magnitude are related to the helicity of the polymer at the measured wavelength. The Faraday rotation and the helical conformation of P3AST are modulated by thermal annealing, which is further supported by DFT calculations and MD simulations. Our results demonstrate that helical polymers exhibit enhanced Verdet constants and expand the previous design space for polythiophene MO materials that was thought to be limited to highly regular lamellar structures. The structure-property studies herein provide insights for the design of next-generation MO materials based upon semiconducting organic polymers.