Optical Faraday Rotation Research Articles

Enhancing chiral molecule detection: A weak measurement approach utilizing two-dimensional information

This study addresses the critical need for high purity chiral molecules in biological systems by overcoming the challenges associated with the quantitative detection of chiral molecules and their enantiomeric mixtures. We developed an innovative detection approach that leverages the two-dimensional information gleaned from natural optical rotation (NOR) and Faraday optical rotation (FOR) under magnetic fields in chiral molecules, combined with an ultrahigh-resolution weak measurement sensor. This novel weak measurement system achieves unparalleled accuracy in detecting spin angles, with a precision of 1.86 × 10−5°. Notably, our method introduces no chemical reactions or interference with the substances under test. It offers enhanced discrimination capabilities through the dual-dimensional analysis of both natural and Faraday optical rotation, alongside a simple and compact sensor design. Conclusively, our study introduces a novel, high-precision, and multi-dimensional optical detection paradigm for chiral molecules. By incorporating Faraday rotation in the presence of a magnetic field, we expand the informational dimensionality accessible to the original weak measurement sensor, facilitating the quantitative analysis of chiral molecules and their enantiomers. This breakthrough not only furnishes a novel instrument for the exploration and development of chiral pharmaceuticals but also propels the advancement of weak measurement sensing technology forward.

Effect of a dynamic axial magnetic field on a preconditioned single-wire Z-pinch

In this study, the effect and mechanism of a dynamic axial magnetic field on a preconditioned single-wire Z-pinch were investigated experimentally and theoretically. Optical diagnostic methods, including shadowgraphy, interferometry, Faraday rotation, and Thomson scattering, have been used to measure the parameters of magnetized plasmas. Compression of the azimuthal and axial magnetic fields was observed, and the suppression of the plasma instability was recorded and analyzed. The results showed that an external axial magnetic field could reduce the plasma instability and non-uniformity, but prolong the implosion time and weaken the compression ratio. In the implosion process with an axial magnetic field, the plasma rotated at a speed similar to that of imploding, which could be regarded as a stabilization method. A simplified model of the diffusion and compression processes of a dynamic axial magnetic field was developed to investigate the conditions for maximizing the amplitude of the axial magnetic field. Subsequently, the snowplow model was used to calculate the effect of axial magnetic fields on the implosion process and energy conversion.

Intensity Equalization of Bidirectional Fiber Laser Based on a Non-Reciprocal Optical Attenuator.

The application of a bidirectional laser requires the laser intensity in both directions to be balanced. However, the CW and CCW light intensities in current bidirectional erbium-doped fiber laser experiments differ due to the gain competition effect. There is no report on equalizing the intensity in the CW and CCW directions. This paper proposes a bidirectional non-reciprocal optical attenuator using the Faraday optical rotation effect. Continuous attenuation adjustment is realized by changing the angle between the polarizer's transmission axis and the linear polarized light. In this study, we analyzed the influence of different parameters on the device's performance, built a non-reciprocal attenuator, and tested the bidirectional attenuation curve, which was consistent with the simulation results. The device was integrated into a bidirectional fiber laser, and the light intensity in both directions was balanced through non-reciprocal adjustment. Combined with closed-loop control, the average intensity difference fluctuation between the two directions was controlled at 0.28% relative to the average power, realizing stable long-term bidirectional fiber laser intensity equalization.

Temperature-Monitored Fibre Optic Current Sensor Using Channelled-Spectrum Analysis

The fibre optic current sensor demonstrated here uses the intrinsic temperature and wavelength dependence of the Verdet constant of a terbium gallium garnet (TGG) magneto-optic material and the two micro-optic linear polarizers attached, to simultaneously extract the values of temperature and the optical Faraday rotation (induced by the presence of the magnetic field due an electric current on a conductor) without any extra optical component attached to the optical sensor head. The simultaneous measurement is achieved by illuminating the sensor head with a broadband optical source and by careful signal processing of the originated channelled-spectrum, compensate the sensor’s temperature dependence.

Theoretical investigation of optical properties and Faraday rotation of one-dimensional periodic structure of magneto-optical material with a defect electro-optical material for the supported Tamm plasmon polaritons

Theoretical investigation of optical properties and Faraday rotation of one-dimensional periodic structure of magneto-optical material with a defect electro-optical material for the supported Tamm plasmon polaritons

Phase-matching condition in rotatory nonlinear optics

Polarization rotation of light beams, such as optical activity and Faraday rotation, is a natural effect that generates the rotation of the polarized direction of light and some undiscovered characteristics in nonlinear optics. In our previous study, we theoretically investigated the second-harmonic generation process in rotatory nonlinear optics and found an unprecedented phase-matching condition. Here, the optical phase-matching condition in the second-harmonic generation with rotatory polarization is theoretically analyzed and associated with the angular rotation-induced phases of mixing waves, which goes beyond the previous theoretical analysis. Moreover, the Pancharatnam-Berry topological phase was found to be periodically generated and could be employed to compensate for the mismatched phase during nonlinear optical interaction. Possible experimental schemes were proposed and discussed. This work provides not only a universal and flexible (quasi-) phase-matching condition for the rotatory nonlinear optics existing in most nonlinear optical media but may also inspire the development of modern photonics.

Optomechanically induced Faraday and splitting effects in a double-cavity optomechanical system

We demonstrate the optomechanically induced Faraday and splitting effects caused by optical mode conversion in a double-cavity optomechanical system. In the scheme, the polarization states of propagating light fields can be arbitrarily tailored to achieve optical Faraday rotation successfully via optomechanical interaction. Meanwhile, the energy-level splitting of the degenerate optical modes leads to the separation of two orthogonal polarization optical modes and the manipulation of spin angular momentum of photons. Moreover, the polarized output component orthogonal to the control field can be manipulated by properly choosing the tunneling interaction between two optical cavities, which enables the complete polarization control of the probe field. Using the polarized control field and optical gain in the auxiliary cavity, we can effectively improve the efficiency of optical Faraday rotation. Finally, we study how to achieve different optical control for different polarization states, which provides an effective method for the implementation of optical isolators in cavity optomechanical systems. Our scheme may benefit future realization of flexible controllability for the vector properties and spin angular momentum of photons, and can promote potential applications in optical nonreciprocal transport, routers, isolators, and circulators.

Time-dependent atomic magnetometry with a recurrent neural network

We propose to employ a recurrent neural network to estimate a fluctuating magnetic field from continuous optical Faraday rotation measurement on an atomic ensemble. We show that an encoder-decoder architecture neural network can process measurement data and learn an accurate map between recorded signals and the time-dependent magnetic field. The performance of this method is comparable to Kalman filters while it is free of the theory assumptions that restrict their application to particular measurements and physical systems.

First-principles study on magneto-optical effects in the ferromagnetic semiconductorsY3Fe5O12andBi3Fe5O12

The magneto-optical (MO) effects not only are a powerful probe of magnetism and electronic structure of magnetic solids but also have valuable applications in high-density data-storage technology. Yttrium iron garnet (Y$_3$Fe$_5$O$_{12}$) (YIG) and bismuth iron garnet (Bi$_3$Fe$_5$O$_{12}$) (BIG) are two widely used magnetic semiconductors with strong magneto-optical effects and have also attracted the attention for fundamental physics studies. In particular, YIG has been routinely used as a spin current injector. In this paper, we present a thorough theoretical investigation on magnetism, electronic, optical and MO properties of YIG and BIG, based on the density functional theory with the generalized gradient approximation plus onsite Coulomb repulsion. We find that both semiconductors exhibit large MO effects with their Kerr and Faraday rotation angles being comparable to that of best-known MO materials such as MnBi. Especially, the MO Kerr rotation angle for bulk BIG reaches -1.2$ ^{\circ}$ at photon energy $\sim2.4$ eV, and the MO Faraday rotation angle for BIG film reaches -74.6 $ ^{\circ}/\mu m$ at photon energy $\sim2.7$ eV. Furthermore, we also find that both valence and conduction bands across the MO band gap in BIG are purely spin-down states, i.e., BIG is a single spin semiconductor. These interesting findings suggest that the iron garnets will find valuable applications in semiconductor MO and spintronic nanodevices. The calculated optical conductivity spectra, MO Kerr and Faraday rotation angles agree well with the available experimental data. The main features in the optical and MO spectra of both systems are analyzed in terms of the calculated band structures especially by determining the band state symmetries and the main optical transitions at the $\Gamma$ point in the Brillouin zone.

Optical Rotation Approach to Search for the Electric Dipole Moment of the Electron

The P , T -odd Faraday effect (i.e., rotation of the polarization plane of light propagating through a medium in presence of the external electric field due to P , T symmetry violating interactions) is considered for several atomic species: Ra, Pb, Tl, Hg, Cs, and Xe. Corresponding theoretical simulation of P , T -odd Faraday experiment, with already achieved intracavity absorption spectroscopy characteristics and parameters, is performed. The results show that the magnetic dipole transitions in the Tl and Pb atoms as well as the electric dipole transitions in the Ra, Hg and Cs atoms are favorable for the observation of the P , T -odd Faraday optical rotation. The estimation of the rotation angle of the light polarization plane demonstrates that recently existing boundaries for the electron electric dipole moment can be improved by one-two orders of magnitude.

A method to measure the in situ magnetic field in a Hall thruster based on the Faraday rotation effect

This paper presents a method to measure the in situ magnetic field in a Hall thruster by optical non-invasive means, based on the optical Faraday rotation effect. This method does not affect the discharge of the thruster. Furthermore, its time resolution depends on the speed of the photo-detector, and measurement at a MHz scale can be achieved.

Magnetism and magneto-optical effects in bulk and few-layer CrI3: a theoretical GGA + U study

The latest discovery of ferromagnetism in atomically thin films of semiconductors Cr2Ge2Te6 and CrI3 has unleashed numerous opportunities for fundamental physics of magnetism in two-dimensional (2D) limit and also for technological applications based on 2D magnetic materials. To exploit these 2D magnetic materials, however, the mechanisms that control their physical properties should be thoroughly understood. In this paper, we present a comprehensive theoretical study of the magnetic, electronic, optical and magneto-optical (MO) properties of multilayers (monolayer (ML), bilayer (BL) and trilayer) as well as bulk CrI3, based on the density functional theory with the generalized gradient approximation plus on-site Coulomb repulsion scheme. Interestingly, all the structures except the BL, are found to be single-spin ferromagnetic semiconductors. They all have a large out-of-plane magnetic anisotropy energy (MAE) of ∼0.5 meV/Cr, in contrast to the significantly thickness-dependent MAE in multilayers of Cr2Ge2Te6. These large MAEs suppress transverse spin fluctuations and thus stabilize long-range magnetic orders at finite temperatures down to the ML limit. They also exhibit strong MO effects with their Kerr and Faraday rotation angles being comparable to that of best-known bulk MO materials. The shape and position of the main features in the optical and MO spectra are found to be nearly thickness-independent although the magnitude of Kerr rotation angles increases monotonically with the film thickness. Magnetic transition temperatures estimated based on calculated exchange coupling parameters, calculated optical conductivity spectra, MO Kerr and Faraday rotation angles agree quite well with available experimental data. The calculated MAE as well as optical and MO properties are analyzed in terms of the calculated orbital-decomposed densities of states, band state symmetries and dipole selection rules. Our findings of large out-of-plane MAEs and strong MO effects in these single-spin ferromagnetic semiconducting CrI3 ultrathin films suggest that they will find valuable applications in semiconductor MO and spintronic nanodevices.

Weak enhanced resonant Faraday rotation in pure cobalt plasmonic lattices: Thickness dependent Faraday rotation studies

The thickness dependent magneto-optical Faraday rotation in Co ferromagnetic thin films and perforated periodic Co nano-hole arrays were investigated. It was observed that the optical response and Faraday rotation of Co nano-hole arrays were strongly dependent on the thickness of the film, and the Faraday rotation reached the maximum amplitude at an optimal thickness value of 30–50 nm, which contrasted with the Co thin films where the Faraday rotation increased with the film thickness. In addition, the Faraday rotation spectra of Co nano-hole arrays showed a weak resonantly enhanced peak at the anti-resonance modes (or Wood’s anomalies) on the transmission spectra, which correspond to the enhanced local electric field at the film and surrounding medium interfaces. All experimental results were confirmed by the finite-difference time domain calculations.

Optical frequency comb Faraday rotation spectroscopy

We demonstrate optical frequency comb Faraday rotation spectroscopy (OFC-FRS) for broadband interference-free detection of paramagnetic species. The system is based on a femtosecond doubly resonant optical parametric oscillator and a fast-scanning Fourier transform spectrometer (FTS). The sample is placed in a DC magnetic field parallel to the light propagation. Efficient background suppression is implemented via switching the direction of the field on consecutive FTS scans and subtracting the consecutive spectra, which enables long-term averaging. In this first demonstration, we measure the entire Q- and R-branches of the fundamental band of nitric oxide in the 5.2–5.4 µm range and achieve good agreement with a theoretical model.

Homogenization of Doppler broadening in spin-noise spectroscopy

The spin noise of cesium atoms vapor with admixture of buffer gas is experimentally investigated by measuring the spin induced Faraday rotation fluctuations in the vicinity of D 2 line. The line, under these conditions, is known to be strongly inhomogeneously broadened due to the Doppler effect. Despite that, optical spectrum of the spin noise power, as we have found, has the characteristic shape of the homogeneously broadened line with the dip at the line center. This fact is in stark contrast with the results of previous studies of inhomogeneous quantum dot ensembles. In addition, the two-color experiments, where correlations of the Faraday rotation fluctuations for two probe wavelengths were measured, have shown, in a highly spectacular way, that these fluctuations are either correlated, or anticorrelated depending on whether the two wavelengths lie on the same side, or on different sides of the resonance. The experimental data are explained within the developed theoretical model which takes into account both kinetics and spin dynamics of Cs atoms. It is shown that the unexpected behavior of the optical Faraday rotation noise spectra and effective homogenization of the optical transition in the spin-noise measurements are related to smallness of the momentum relaxation time of the atoms as compared with their spin relaxation time.

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.

Synthesis and properties of nanocrystal BiPO4 in diamagnetic PbO-Bi2O3-B2O3 glass

In this study, we synthesized of BiPO4 nanocrystals in diamagnetic glass (45PbO–45Bi2O3–8B2O3–2P2O5mol %) by melt quenching technique and studied its influence to glass Faraday rotation. The 9nm irregular BiPO4nanocrystals formed in glass and changed glass structure, spectral and properties through the characterization of X-ray diffraction, field Emission scanning electron microscopy, differential scanning calorimetry, UV–Vis optical absorption, Vicker's hardness and Verdet constant etc. The BiPO4 –induced local plasmon effect and bigger polarization gave glass improvements on optical cutoff wavelength, Faraday rotation and Vicker's hardness which is very attractive to magneto optical glass devices.

Structures and magneto optical property of diamagnetic TiO2-TeO2-PbO-B2O3 glass

TiO2 doped diamagnetic 50.8TeO2-29.2PbO-(20−x)B2O3: xTiO2 (where x=0, 2, 5, 10, 15 and 20mol% respectively) glasses were synthesized and characterized in terms of their glass forming, structure, spectra and Faraday rotation using a home-made optical bench. The doped TiO2 not only decreased glass transition temperatures, but also increased refractive index, Vickers hardness (352HV), optical cutoff wavelength (458nm) and Faraday rotation (0.2043min/G·cm) at 632.8nm wavelength.

Making unpolarized light sensitive to polarization-sensitive devices

Here we propose a novel scheme in which depolarized or unpolarized light can respond to polarization-dependent optical elements such as an input-polarization-dependent wavelength-selective filter. An optical apparatus for realizing the proposed scheme consists of a polarization beam splitter, two Faraday rotators, and four waveplates. By harnessing the polarization decomposition/superposition property of a polarization-diversity loop and the irreciprocity of optical Faraday rotation, we could make unpolarized light selectively excite one of the two principal axes of a polarization-dependent element like polarized one while maintaining the unpolarized nature. The principle of operation of this apparatus was theoretically analyzed through the investigation of the polarization variation of light passing through the optical elements comprising it. Then, its polarization-selective feature was experimentally verified by employing a long-period fiber grating inscribed on polarization-maintaining fiber, which had polarization-dependent spectral dips with different resonance wavelengths, as a polarization-dependent element in the polarization-diversity loop. One of the two spectrally separated resonances of the grating could be freely chosen through the proper control of the waveplates in the apparatus.

Compact quantum gates for hybrid photon–atom systems assisted by Faraday rotation

We present some compact circuits for a deterministic quantum computing on the hybrid photon---atom systems, including the Fredkin gate and SWAP gate. These gates are constructed by exploiting the optical Faraday rotation induced by an atom trapped in a single-sided optical microcavity. The control qubit of our gates is encoded on the polarization states of the single photon, and the target qubit is encoded on the ground states of an atom confined in an optical microcavity. Since the decoherence of the flying qubit with atmosphere for a long distance is negligible and the stationary qubits are trapped inside single-sided microcavities, our gates are robust. Moreover, ancillary single photon is not needed and only some linear-optical devices are adopted, which makes our protocols efficient and practical. Our schemes need not meet the condition that the transmission for the uncoupled cavity is balanceable with the reflectance for the coupled cavity, which is different from the quantum computation with a double-sided optical microcavity. Our calculations show that the fidelities of the two hybrid quantum gates are high with the available experimental technology.