Magneto-optical Media Research Articles

Near-infrared multi-band small-angle TE-polarization nonreciprocal thermal emitter

Multi-band small-angle irreversible radiation is significantly demanded in applications of high-resolution infrared sensing and infrared filtering. However, current nonreciprocal thermal radiation is either multichannel radiating with large incident angles or radiating at small angles within one single band. To address this issue, a multi-band nonreciprocal thermal emitter operated by exciting multiple resonances within the near-infrared band is proposed. The adopted microstructure arrays consist of periodic silicon square-ring arrays that are supported by magneto-optical medium and metal layer. With the physical mechanisms study through electromagnetic field energy distribution, the TE-polarized multi-band nonreciprocity of thermal radiation is over 70 % at small incident angle of 4°. Equally important, this strategy is effective and generalizable for dual-polarized small-angle multi-band nonreciprocal radiation with adopted microstructure arrays. It is believed that this scheme can promote the development of nonreciprocal thermal photonics.

Thermomagnetic recording of highly Bi-substituted iron garnet film using scanning laser for spatial light modulation

Spatial light modulations (SLM) utilizing the magneto-optical (MO) effect of magnetic materials are expected to offer fast switching and small pixel sizes as small as the wavelength of the light. However, the small MO effect is a major issue. In this paper, we report a thermomagnetic recording of highly bismuth-substituted garnet film, known for large Faraday effects. Y0.5Bi2.5Fe4GaO12 (Bi,Ga:YIG) film with a Faraday rotation of −4.66 degrees was used as an MO medium. A laser scanning thermomagnetic recording system using a Galvanometer mirror was developed and the size and quality of recorded magnetic domains were investigated. The smallest recorded magnetic domain diameter was 0.62 μm with a small standard deviation of 0.09 μm. Line patterns with a width of 1 μm can be recorded in this film. We found that Bi,Ga:YIG films have potential as a material for SLMs with fast switching, submicron pixel size, and large MO effect.

Toward nanophotonic optical isolation via inverse design of energy transfer in nonreciprocal media

In this paper we generalize the adjoint method of inverse design to nonreciprocal media. As a test case, we use three-dimensional topology optimization via the level-set method to optimize one-way energy transfer for pointlike source and observation points. To achieve this we introduce a suite of tools, chiefly what we term the “Faraday-adjoint” method which allows for efficient shape optimization in the presence of magneto-optical media. We carry out an optimization based on a very general equation that we derive for energy transfer in a nonreciprocal medium, and link finite-different time-domain numerics to analytics via a modified Born series generalized to a tensor permittivity. This paper represents a stepping stone towards practical nanophotonic optical isolation, often regarded as the “holy grail” of integrated photonics. Published by the American Physical Society 2024

Quantum torque on a non-reciprocal body out of thermal equilibrium and induced by a magnetic field of arbitrary strength

AbstractA stationary body that is out of thermal equilibrium with its environment, and for which the electric susceptibility is non-reciprocal, experiences a quantum torque. This arises from the spatially non-symmetric electrical response of the body to its interaction with the non-equilibrium thermal fluctuations of the electromagnetic field: the non-equilibrium nature of the thermal field fluctuations results in a net energy flow through the body, and the spatially non-symmetric nature of the electrical response of the body to its interaction with these field fluctuations causes that energy flow to be transformed into a rotational motion. We establish an exact, closed-form, analytical expression for this torque in the case that the environment is the vacuum and the material of the body is described by a damped oscillator model, where the non-reciprocal nature of the electric susceptibility is induced by an external magnetic field, as for magneto-optical media. We also generalise this expression to the context in which the body is slowly rotating. By exploring the high-temperature expansion of the torque, we are able to identify the separate contributions from the continuous spectral distribution of the non-reciprocal electric susceptibility, and from the resonance modes. In particular, we find that the torque persists in the limiting case of zero damping parameter, due to the contribution of the resonance modes. We also consider the low-temperature expansion of the torque. This work extends our previous consideration of this model to an external magnetic field of arbitrary strength, thereby including non-linear magnetic field effects.

Para- and dia-magnetization distribution via localization of atom by absorption and magnetic loss

A high magneto-optical medium is used to modify atom localization by magnetic loss and absorption spectrum with para and dia magnetization distribution. The localization is investigated in the range of or distance along x-axis and y-axis. Dia-magnetization hole is investigated within the range along x-axis and y-axis. Crater-type atom localization peak is reported by a magnetic loss, and a burner-like localization peak is investigated by absorption with dia-magnetization hole distribution. A para-magnetization hole is also investigated in the range of . Gaussian-type atom localization peaks are investigated by both magnetic loss and absorption spectrum in the para-magnetization hole region. Depth and grave-type atom localization is also reported in the para and dia-magnetic region by absorption and magnetic loss spectrum.

Manipulation of sensitivity of the surface plasmon polariton waves at the interface of high magneto-optical medium and silver metal using angular interrogation

In this manuscript, sensitivity of the surface plasmon polariton waves (SPPs) using angular interrogation is coherently manipulated at the interface of four level high magneto-optical medium and silver metal using prism geometry. The control and probe fields detuning, Rabi frequency and decay rate manipulated significantly the angular interrogation of sensitivity of the surface plasmon polariton waves. The permittivity ϵd and permeability μd of the high magneto-optical medium play an important role in the manipulation of the sensitivity. The sensitivity is a function of control field detuning. The maximum sensitivity is reported to 800 deg/RIU with control field detuning. The minimum sensitivity is investigated to 6 deg/RIU with probe field detuning and Rabi frequency of control field. The reported results have useful applications in data storage and chemical sensing technologies.

Asymmetric Magneto-Optical Rotation in Magnetoplasmonic Nanocomposites

The results of the asymmetric magneto-optical rotation in the magnetoplasmonic nanocomposite study are presented. The asymmetry is observed in spectra of magneto-optical rotation when a magneto-optical medium with a plasmonic subsystem is magnetized along or against the radiation wave vector. The asymmetry is observed as vertical displacement of a magneto-optical hysteresis loop too. Such asymmetry is detected in magnetoplasmonic nanocomposite, which consists of a magneto-optical layer of Bi substituted iron-garnet intercalated with a plasmonic subsystem of gold self-assembled nanoparticles. It is shown that the physical reason for the asymmetric magneto-optical rotation is the manifestation of the Cotton–Mouton birefringence effect when the normal magnetization of the sample to a radiation wave vector appears due to the magnetic component of the electromagnetic field of resonating nanoparticles. This effect is additive to the basic magneto-optical Faraday Effect.

Structure microscopy of an atom in high magneto-optical medium based on transmission and reflection spectra

A five level atomic medium driving by probe and standing waves control fields having dielectric function $$\epsilon _r$$ and permeability function $$\mu _r$$ is placed in a cavity of dielectric function $$\epsilon _1$$ . The permittivity and permeability functions are directly related to the reflection and transmission spectra of the medium. The reflection and transmission spectra of the medium provide information about internal structure and properties of the atom. A central peak/depth is reported in the reflection and transmission spectra, which corresponds to the nuclear region of an atom. Around the central peak/depth regions, circular ring type patterns in the reflection and transmission spectra are reported. These ring type patterns exhibit atomic shells of the atoms. The theoretical investigation of internal structure microscopy of an atom have potential applications in nano-lithography and atoms trapping. Our proposed model might be helpful for increasing the capability of optical microscopy and atoms imaging.

Thermal lens in magneto-active ZnS, ZnSe and CdSe semiconductor media

Thermal lens in zinc selenide (ZnSe), cadmium selenide (CdSe) and zinc sulfphide (ZnS) magnetooptical media was investigated by phase-shifting interferometry. It was shown that the thermal lens in ZnSe is 10 times weaker and in ZnS and CdSe are 2 and 16 times higher than in popular magnetooptical terbium gallium garnet crystal. The focal shift and thermo-optical characteristics and of magneto-optical figure of merit were determined. The obtained values of absorption coefficient 1.1х10−4 cm−1 allowed determining a record, 4 kW maximum operating power of a ZnSe Faraday isolator.

Light transport through a magneto-optical medium: simple theory revealing fruitful phenomena.

Electromagnetic wave transmission in a magneto-optical (MO) medium is a basic and old topic but has raised new interest in recent years, because MO medium plays a vital role in optical isolator, topological optics, electromagnetic field regulation, microwave engineering, and many other technological applications. Here, we describe several fascinating physical images and classical physical variables in MO medium by using a simple and rigorous electromagnetic field solution approach. We can easily obtain explicit formulations for all relevant physical quantities, such as the electromagnetic field distribution, energy flux, reflection/transmission phase, reflection/transmission coefficients, and Goos-Hänchen (GH) shift in MO medium. This theory can help to deepen and broaden our physical understanding of basic electromagnetics, optics, and electrodynamics in application to gyromagnetic and MO homogeneous medium and microstructures, and might help to disclose and develop new ways and routes to high technologies in optics and microwave.

A device of XOR logic gate and multiscale sensing based on layered topology

In this paper, a multiscale non-reciprocity device based on the layered topology of one-dimensional (1-D) photonic crystals is studied, which can meet the functions of XOR logic gate, magnetic field sensing and refractive index sensing. Modulating by the external magnetic fields, sharp transmission peak (TP) is obtained in the terahertz (THz) range (the value of TP is more than 0.9), by changing the two different magnetic fields applied to the particular medium layers, TP enables XOR logic phenomena at the same frequency point. Simulation shows that with the detection of physical quantities changes, the frequency point of TP will vary. Therefore, through the location of TP, the sensing functions of magnetic field and refractive index can be realized, moreover the optimum performances of quality factor (QF), sensitivity (S), the figure of merit (FOM), and the detection limit (DL) belonging to them are 1323.45, 0.01 (2πc/d 0)/T, 35.93 T−1, 1.39 × 10−3 T and 1381.88, −0.0061 (2πc/d 0)/RIU, 13.57 RIU−1, 3.7 × 10−3 RIU. Additionally, the device also realizes the non-reciprocity of electromagnetic waves (EWs) via the introduction of magneto-optical media InSb and the change of EWs incident angle, which means that XOR logic gate, magnetic field, and refractive index sensing detection respectively have positive and negative scales.

Nonreciprocal propagation of surface electromagnetic waves in structures comprising magneto-optical materials

This paper investigates theoretically the effect of nonreciprocity on surface electromagnetic waves (SEWs) propagating in magneto-optical structures in mutually opposite directions, i.e., on waves with tangential wave numbers $k$ of opposite sign. Namely, of our interest is a correlation between the numbers of forward ($k>0$) and backward ($k<0$) propagating SEWs, which manifests itself as a limit on the total number of SEWs. The peculiarity of this limit is that the maximum total number of forward- and backward-propagating SEWs is less than the sum of the maximum numbers of SEWs for each of the opposite directions taken individually. We derive a relation between the electromagnetic surface impedances relevant to forward- and backward-propagating waves. Afterward, by using general properties of these impedances valid regardless of the crystallographic symmetry, we analyze the roots of dispersion equations without solving them explicitly. Various types of magneto-optical structures are considered. In particular, it is shown that, in the bicrystal formed of two half-infinite magneto-optical media, the maximum total number of forward- and backward-propagating SEWs is two at a given value of $|k|$, whereas in each of the mutually opposite directions two SEWs can exist. For example, if two forward-propagating SEWs are known to exist, then no backward-propagating SEW exists. In the case where a metal film is inserted between two different half-infinite magneto-optical media, the maximum number of SEWs in one direction is four but the maximum of the total number of forward- and backward-propagating SEWs is six rather than eight.

Spectral nonreciprocal optical properties and enhancement effects based on SiC magneto-optical porous medium

In this work, a three-dimensional periodic ordered microrod porous structure is used to model the SiC magneto-optical porous medium. The nonreciprocal optical properties of the monolayer and multilayer porous structures are studied in the infrared band. The effects of the structure parameters, such as round rib height, rib diameter and layer number, are predicted by applying the FDTD method to analyze the nonreciprocal absorptance. And the characteristics of absorption spectra based on the optimized porous structure by adding air columns into the microrods are further studied. The nonreciprocal absorptance of these two porous structures was compared at different incident angles and different magnetic field intensities, and it was discovered that the smaller angle of incidence, the stronger nonreciprocal effect. Moreover, the enhanced nonreciprocal absorptance of these two porous structures is described as the contour plot of the electrical field intensities, in which the physical mechanism is also explained. It is found that the addition of air columns can effectively increase the absorptive capacity of the structure and enhance the nonreciprocal absorption in the infrared wavelength range.

Nonlinear Surface Polaritons near the Interface between a Magneto-Optical Substance and a Nonlinear Metamaterial with a Permittivity Close to Zero

Relevance. Considerable attention of researchers is drawn to nonlinear surface optical waves, as they are promising for application in optical information processing systems, ultra-sensitive sensors, and modern telecommunications components. Purpose. To obtain an exact solution of the Maxwell equation system for TM-polarised nonlinear surface polaritons propagating along the interface between an optically linear magnetic medium and an optically nonlinear medium with saturated nonlinearity. Methods. Analysis of the properties of nonlinear surface polaritons (NSP) and mathematical modelling of the dependence of the permittivity of a nonlinear medium on the intensity are used. Results. TM-polarised nanoparticles propagating along the interface of a magneto-optical medium and a nonlinear optical metamaterial with a permittivity close to zero (ENZ-metamaterial) are studied. For NSP in such a structure, an exact solution of the Maxwell equation system is obtained, considering the saturation effect of optical nonlinearity. On this basis, the dependences of constant propagation on the total energy flux of NSP and energy fluxes in contact media in the structure were investigated: magneto-optical ENZ-metamaterial with negative permittivity/nonlinear self-focusing ENZ-metamaterial. Conclusions. The NSP energy flow is positive in a nonlinear medium and negative in a linear one. As the saturation level decreases, the NSP energy fluxes in the contacting media increase modulo, if the value of the NSP propagation constant (NSPPC) is fixed. The lowest NSPPC value for guiding nonlinearity is obtained when the total energy flow of the NSP becomes zero. As the saturation level decreases, the NSP propagation variable (NSPPV) increases. At a fixed NSPPC, with a decrease in the magnetic permeability, the energy fluxes of NSP in the contacting media increase. When the magnetic permeability decreases to zero and the NSP energy flux is positive, the NSPPV change range narrows

Magneto-optical nonreciprocity without chirality: Archimedean spirals on InSb.

We report the observation of magneto-optical nonreciprocity in Faraday geometry in a hybrid metamaterial consisting of an Archimedean spiral metasurface and semiconductor InSb that serves as the magneto-optical medium. None of the metamaterial constituents possesses chirality, which is usually a necessary ingredient for optical nonreciprocity in natural materials when the light travels along the magnetic field direction. We also find that our metamaterial can serve as an optical element for polarization control via magnetic field. Another significant property of our hybrid metamaterial is the emergence of the four different transmittance states, which are observed for the four combinations of the positive and negative magnetic field and the direction of the wavevector of light.

Magnetic Emulsions as Prospective Magneto-Optical Media

The optical properties of magnetic emulsions with microdroplets of a magnetic fluid in hydraulic oil under the influence of a magnetic field are investigated. It is shown that the optical transmittance of a magnetic emulsion can be controlled by changing the strength and direction of the magnetic field. With prolonged exposure to a magnetic field, diffraction of light occurs in a magnetic emulsion, the intensity and shape of the diffraction pattern are determined by the field parameters. It is shown that magnetic emulsions can be a promising medium for controlled neutral optical filters and magneto-optical sensors.

Near-Field Energy Transfer between Graphene and Magneto-Optic Media.

We consider the near-field radiative energy transfer between two separated parallel plates: graphene supported by a substrate and a magneto-optic medium. We first study the scenario in which the two plates have the same temperature. An electric current through the graphene gives rise to nonequilibrium fluctuations and induces energy transfer. Both the magnitude and direction of the energy flux can be controlled by the electric current and an in-plane magnetic field in the magneto-optic medium. This is due to the interplay between the nonreciprocal photon occupation number in the graphene and nonreciprocal surface modes in the magneto-optic plate. Furthermore, we report that a tunable thermoelectric current can be generated in the graphene in the presence of a temperature difference between the two plates.

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.

Compensation for Thermally Induced Depolarization in Magneto-Optical Media Made of Materials With a Negative Optical Anisotropy Parameter

Thermally induced depolarization of radiation is the principal limiting factor of using Faraday devices in laser radiation with a high average power. In this work thermally induced depolarization is analyzed in a system of two optical elements made of cubic magneto-optical materials with a negative optical anisotropy parameter separated by a quartz rotator. The parameters of the optical scheme of a Faraday isolator (FI) based on single crystals cut in the [C] orientation, at which effective compensation of thermally induced depolarization is realized, are found. These parameters are universal and do not depend on the material of the magneto-optical element. Analytical expressions for the integral thermally induced depolarization are derived and the contributions of thermally induced linear birefringence and of the temperature dependence of the Verdet constant are analyzed. The parameter that allows assessing the contributions to depolarization of each of the thermal effects and predicting the efficiency of using the compensation scheme for a specific magneto-optical material is introduced. The proposed FI scheme with compensation is investigated for a number of known magneto-optical materials possessing a negative optical anisotropy parameter. The results obtained will significantly reduce thermally induced polarization distortion of radiation, and will allow developing FIs providing a high isolation ratio in powerful laser radiation.

Thermo-optical properties of cryogenically cooled (Tb[formula omitted]Y[formula omitted])[formula omitted]O[formula omitted] ceramics

Due to a high Verdet constant and paramagnetic properties, the ceramics based on terbium oxide is a promising candidate as a magneto-optical medium for developing cryogenic Faraday isolators. Cryogenic cooling suppresses thermal effects and leads to an increase in the maximum power of the laser radiation passing through the Faraday isolator at the same isolation ratio. We have measured the thermally-induced depolarization and the thermal lens within the 81–297 K temperature range and the linear absorption coefficient α0 within the 83–297 K temperature range in (Tb0.9Y0.1)2O3. The ratio of the effective thermo-optical constants Peff/Qeff was ∼6.44 in the studied temperature region. On cooling to LN2 temperature, the parameters α0Qeff/κ and α0Peff/κ (κ is the thermal conductivity coefficient) decreased by a factor of ∼5.2. The α0 was temperature independent. The results of the study demonstrate great prospects for the use of terbium oxide based ceramics in cryogenic Faraday isolators.