Transverse Magneto-optical Kerr Effect Research Articles

Enhancement of transverse magneto-optical Kerr effect using transition metals in a grating-based gyro-electric structure

Abstract This study proposes a new structure based on a grating with magneto-optical properties and a layer of transition metals (platinum, silver, copper, gold, and palladium). The research aims to investigate the impact of surface plasmon polaritons on enhancing the transverse magneto-optical Kerr effect when exposed to TM- and TE-polarized waves. After optimizing the structure’s dimensions, it was determined that the transition metal layer should have a thickness of 20 nm. The study involves applying TM- and TE-polarized light to the structure to observe variations in reflected light and the transverse magneto-optical Kerr effect. The findings reveal that the gyro-electric magneto-optics material responds to TMpolarized waves, and silver and gold are identified as the most effective metals for the proposed structure.

Transverse magneto-optical Kerr effect enhancement in si–ni nanogratings by mie and surface lattice resonances

We demonstrate experimentally that a one-dimensional array of silicon nanowires periodically placed on a nickel substrate enhances the transverse magneto-optical Kerr effect (TMOKE) compared to a nickel film. The enhancement mechanism is associated with the excitation of two types of resonances: multipole Mie resonances in each nanowire and surface lattice resonances (SLRs) emerging from the periodic arrangement of the nanowires. The maximal TMOKE values reached up to 1.9 % and 2.6 % due to the excitation of SLR and a magnetic dipole resonance, respectively. When the SLR is excited, the spectral width of the TMOKE enhancement is narrower compared to the case of the magnetic dipole resonance.

Achieving a comparable transverse magneto-optical Kerr effect by spin–orbit field driven magnetoplasmonic

In this study, we propose and simulate a magnetoplasmonics heterostructure that utilizes spin–orbit fields to generate an internal magnetic field and create a significant magneto-optical effect. Our approach offers a new way to overcome the challenges of using permanent magnets or magnetic coils in conventional magnetoplasmonics, such as high-power consumption and non-scalability. We demonstrate that it is possible to create an appropriate amount of magnetic field using spin–orbit fields induced by the spin-Hall effect, such that the consumption power becomes reasonable and the dimensions could be miniaturized. This approach will be an important development in the field of magneto-optics, as it can lead to enhanced transverse magneto-optical Kerr effect in the present of surface plasmon polaritons. The proposed nanostructure consists of a ferromagnetic film adjacent to a heavy metal layer, both sandwiched between two noble metal films, and deposited on a dielectric prism. The strength of the Kerr signal strongly depends on the thickness of the ferromagnetic layer, with the maximum effect observed at a thickness of 5nm. This concept has potential for various nanophotonic and spintronic applications, particularly for developing high-speed active plasmonic devices for ultrafast light modulation.

Transverse magneto-optical Kerr effect enhanced by surface plasmon resonances at the critical coupling condition

Nanostructures possessing plasmonic and magnetic properties can enhance the transverse magneto-optical Kerr effect (TMOKE) by exciting surface plasmon resonances (SPRs). This provides a promising platform for magneto-optical SPR sensors with significantly improved sensing performance. Here, we propose a high-performance magneto-optical SPR sensor, which consists of a bilayer Au/Co grating placed on a gold film. By tuning the structural parameters, a Fano-like TMOKE spectrum with a linewidth of only 0.0135 nm and an amplitude approaching the theoretical maximum is obtained. We attribute the optimal TMOKE signal achieved by the sensor to the critical coupling concept which is associated with the trade-off between scattering and intrinsic decay rates of the system. The optimized nanostructure sensor demonstrates a sensitivity of 1432 nm/RIU to refractive index fluctuations as small as 0.0001 in air, and all figures of merit (FOM) up to 105 RIU−1, making it suitable for gas sensor fabrication.

Broadband Enhancement of Magneto-Optical Effects in Hybrid Waveguide-Plasmonic Surfaces for Sensing.

Conventional magnetophotonic nanostructures typically function within narrow wavelength and incident angle ranges, where resonance is observed and magneto-optical (MO) effects are amplified. Expanding these operational ranges may allow for improved applications, including in (bio)sensing devices. In this study, we describe a hybrid magnetoplasmonic waveguide grating (HMPWG) in which the coupling of plasmonic resonances and waveguide modes leads to enhanced MO effects and sensitivity, according to full-wave electromagnetic simulations. High transverse magneto-optical Kerr effect (TMOKE) signals were observed for the full range of wavelengths and angles investigated, i.e., for θinc ≥ 1° and 500 nm ≤ λ ≤ 850 nm. As a proof-of-concept we verified that using the HMPWG nanostructure with an aqueous solution as superstrate one may obtain a sensitivity in variation of the refractive index unit (RIU) of S = 166°/RIU and S = 230 nm/RIU in angle and wavelength interrogation modes, respectively. Upon comparing with conventional magnetoplasmonic gratings, which only enable excitation of plasmonic resonances, we demonstrate that HMPWG nanostructures can be further optimized to reach not only high sensitivity but also high resolution in sensing and biosensing.

Toward Machine-Learning-Accelerated Design of All-Dielectric Magnetophotonic Nanostructures.

All-dielectric magnetophotonic nanostructures are promising for integrated nanophotonic devices with high resolution and sensitivity, but their design requires computationally demanding electromagnetic simulations evaluated through trial and error. In this paper, we propose a machine-learning approach to accelerate the design of these nanostructures. Using a data set of 12 170 samples containing four geometric parameters of the nanostructure and the incidence wavelength, trained neural network and polynomial regression algorithms were capable of predicting the amplitude of the transverse magneto-optical Kerr effect (TMOKE) within a time frame of 10-3 s and mean square error below 4.2%. With this approach, one can readily identify nanostructures suitable for sensing at ultralow analyte concentrations in aqueous solutions. As a proof of principle, we used the machine-learning models to determine the sensitivity (S = |Δθres/Δna|) of a nanophotonic grating, which is competitive with state-of-the-art systems and exhibits a figure of merit of 672 RIU-1. Furthermore, researchers can use the predictions of TMOKE peaks generated by the algorithms to assess the suitability for experimental setups, adding a layer of utility to the machine-learning methodology.

Dielectric crystal coupled with guided-mode resonance to enhance the magneto-optical Kerr effect and sensing behavior in transmission mode

In this study, we introduce a high-performance magneto-optical sensor that features enhanced amplitude and sensitivity, achieved through guided-mode resonance (GMR) excitations in an aluminum antimonide slab. This advancement is facilitated by a square, periodically arranged nanorod structure comprising dielectric materials. The electromagnetic field distributions were obtained along with the transmission spectra to elucidate the GMR mode in our proposed structure, thereby highlighting the enhancement of the transverse magneto-optical Kerr effect (TMOKE) signal in the transmitted mode and the corresponding sensing performance. The findings demonstrate that the position of the TMOKE resonance is remarkably responsive to variations in the background refractive index, yielding an impressive sensitivity of 188.7° per refractive index unit, coupled with a narrow linewidth owing to the inherent low loss of dielectric materials. This investigation lays the groundwork for novel advancements in linear optics, integrated optical circuits, and low-loss biosensing applications.

Magnetic properties and magnetoresistance of hybrid multilayer nanostructures {[(Co40Fe40B20)34(SiO2)66]/[ZnO]}n

The structural, electrical, magnetic, magneto-optical properties and magnetoresistance of {[(Co40Fe40B20)34(SiO2)66]/[ZnO]}n multilayer structures, where n = 50 is the number of bilayers (Co40Fe40B20)34(SiO2)66 nanocomposite and ZnO have been studied. The thicknesses of (Co40Fe40B20)34(SiO2)66 nanocomposite layers as well as ZnO spacers were varied in a wide range. The samples were synthesized by ion-beam sputtering onto glass ceramic substrates. The (Co40Fe40B20)34(SiO2)66 composite have an amorphous structure and the semiconductor ZnO interlayers have a hexagonal crystalline structure with the p63mc symmetry group. The nanocomposite layers containing a ferromagnetic component far from the percolation threshold are in a superparamagnetic state. The presented in the paper data of magnetization, magneto-optical transverse Kerr effect and magnetoresistance indicates that long-range ferromagnetic order does not form down to 77 K both for references ZnO films and studied multilayers with thin and thick ZnO interlayers. An increase in the magneto-optical signal in multilayers compared to references (Co40Fe40B20)34(SiO2)66 composite films has been detected at 1.2 eV. The magnetoresistance of {[(Co40Fe40B20)34(SiO2)66]/[ZnO]}n multilayers with thick (>32 nm) ZnO interlayers is lower than in reference (Co40Fe40B20)34(SiO2)66 nanocomposite, while at thin ZnO interlayers magnetoresistance is significantly higher and reaches 12 % at temperatures of 77 К. Possible mechanisms of ferromagnetic and antiferromagnetic ordering, enhancement of the magneto-optical response and magnetoresistance in {[(Co40Fe40B20)34(SiO2)66]/[ZnO]}n multilayer nanostructures are discussed.

Hybrid magneto-plasmonic structure consisting of hexagonal periodic nanodisks array with giant transverse magneto-optical Kerr effect for sensing application

The present study proposes a theoretical design of the magneto-optical surface plasmon resonance (MOSPR) refractive index sensor that utilizes a magnetic field for modulating the dispersion of surface plasmon. This sensor based on the transverse magneto-optical Kerr effect (TMOKE) is constructed using a hybrid magneto-plasmonic film covered with an array of hexagonal periodic Au nanodisks. The structural parameters were optimized to obtain the Fano shape TMOKE response characterized by an extremely narrow bandwidth (0.00997°) and remarkably high amplitude (0.99). The excitation of the optimal surface plasmon resonance (SPR) and the resonance enhancement effect of multi-mode coupling enables us to achieve a surface sensitivity of 207.5 deg RIU−1 and a high figure of merit of the order of 104 RIU−1, surpassing conventional SPR and MOSPR sensors by at least one order of magnitude. The present study offers a comprehensive guideline for the design of high-performance magneto-plasmonic sensors, facilitating instrument miniaturization and manufacturing cost reduction.

Magneto-optical efficiencies combined with surface-plasmon resonance in FeSi/Au system

We designed and fabricated our original laminated materials that simultaneously exhibited different properties: magneto-optical (MO), i.e., the transverse MO Kerr effects (T-MOKE) and surface-plasmon resonance (SPR). The material design was composed of dielectric, magnetic, and noble-metal layers. We selected the soft-magnetic FeSi thin film as a T-MOKE magnetic layer, while an Au thin film was chosen as a SPR-source layer, creating an FeSi-/Au-based “MO-SPR material.” Strong interactions between T-MOKE and SPR were demonstrated. When the material is irradiated with a laser beam of wavelength 660 nm, at the SPR angle to the material, θR, the highest T-MOKE value was attained. The T-MOKE was markedly enhanced at θR: ∼32 to ∼84 times higher compared with the FeSi single layer (reference). The T-MOKE was amplified by a strong interaction between MO activities and electromagnetic field distributions. The FeSi (5.0 nm)/Au (14.8 nm) specimen achieved the best signal-to-noise ratio (SNR). The sample was then tested for its sensing efficiency by measuring the T-MOKE using distilled water and a glucose solution, respectively: It was possible to distinguish between two different solutions. Our MO-SPR materials utilizing both magnetism and near-field light are thus sufficiently sensitive to be applicable as sensing materials. Furthermore, the polarity of the T-MOKE signal is flipped under the application of a small, external magnetic field owing to the soft magnetism of the FeSi T-MOKE layer. This is highly advantageous to create high-frequency AC-magnetic synchronized T-MOKE sensing systems with low-power consumption.

Relationship between magnetic asymmetry and magnetization in ultrafast transverse magneto-optical Kerr effect spectroscopy in the extreme ultraviolet spectral range

Relationship between magnetic asymmetry and magnetization in ultrafast transverse magneto-optical Kerr effect spectroscopy in the extreme ultraviolet spectral range

Design of a high-resolution magneto-plasmonic biosensor for analyte detection

This paper introduces the design of a magneto-plasmonic refractometric sensor aimed at achieving high resolution. This sensor consists of arrays of gold nanowires and layers of SiO2 and Co6Ag94, where the analyte is placed on the gold nanowires. A p-polarized optical field with a wavelength of 631 nm is used to excite the structure, which is applied in the range of 1° to 45°. A magnetic field is applied to z-axis to create the magneto-optical effect. The reflected optical field of the samples is used to calculate the signal of the transverse magneto-optical Kerr effect, which shows significant changes in the refractive index of the samples and the direction of the magnetic field. The highest displacement is 4°. The highest value of the figure of merit is 3611 RIU−1, and the maximum sensitivity is obtained as 71 °/RIU.

Magnetically tunable Brewster angle in uniaxial magneto-optical metamaterials for advanced integration of high-resolution sensing devices.

In this Letter, we introduce a concept to produce high-resolution, highly integrable biosensing devices. Our idea exploits the highly absorbing modes in multilayered metamaterials to maximize the transverse magneto-optical Kerr effect (TMOKE). Results are discussed in the context of dielectric uniaxial (ε eff,∥ ε eff,⊥>0) and hyperbolic metamaterial (ε eff,∥ ε eff,⊥<0) regimes. For applications in gas sensing, we obtained sensitivities of S = 46.02 deg/RIU and S = 73.91 deg/RIU when considering the system working in the uniaxial and hyperbolic regimes, respectively, with figures of merit (resolution) in the order of 310 or higher. On the contrary, when considering the system for biosensing applications (incidence from an aqueous medium), we observed that the proposed mechanism can only be successfully used in the uniaxial regime, where a sensitivity of 56.87 deg/RIU was obtained.

Unconventional Transverse Magneto‐Optical Kerr Effect in Cobalt Nanopillar Arrays

AbstractNovel magneto‐optical (MO) properties can be actualized through well‐designed nanostructures, greatly improving the application value of MO effects. As only p‐polarized light can generate transverse magneto‐optical Kerr effect (TMOKE) in traditional MO materials, it is quite challenging and valuable to effectuate TMOKE under s‐polarization incidence at optical frequencies. The constructed nanopillar structures in this work can realize a clear TMOKE under both s‐polarization and p‐polarization incidences, as proved by experiments and simulations. Under s‐polarized incident light with an elevation angle of 45°, electric dipole resonance (EDR) and electric quadrupole resonance (EQR) are excited, resulting in the significant enhancement of TMOKE (five orders of magnitude higher than for the planar Co film). The intensity of s‐polarized TMOKE shows an increase with the enhancing diameter and height of the nanopillar structure. The amplitude of p‐polarized TMOKE is also appreciably increased due to the excitation of surface plasmon polaritons (SPPs) and localized surface plasmons (LSPs). Moreover, the Fe and Ni nanopillars display similar reflectivity and s‐polarized TMOKE behaviors in simulations. The s‐polarized TMOKE is unexpectedly observed in ferromagnetic metals for the first time, which builds up a considerable platform for the development and application of novel MO phenomena.

Enhancement of Transverse Magneto-Optic Kerr effect in subwavelength all-dielectric guided mode gratings with a buffer layer

We demonstrate a simple subwavelength all-dielectric photonic device with greatly enhanced transverse magneto-optical Kerr effect (TMOKE) in the transmission mode. The concept utilizes the diffracted waves of the periodic magnetic material bismuth-substituted iron garnet grating to excite the guided mode in the planar waveguide, and adds a buffer layer under the all-dielectric guided mode grating. In the study, it was found that increasing the refractive index of the buffer layer can reduce the coupling between the grating and the waveguide, so that full width at half maximum of the transmission spectra can be narrowed, and the value of TMOKE can be greatly enhanced up to 1.82. It is worth noting that the TMOKE value of the guide mode grating with buffer layer is 3 times that of those without buffer layer, thus opening up different avenues for designing efficient, integrated and low-loss magneto-optical devices. Enhanced TMOKE has great potential for applications such as biosensing/high-resolution sensing, magneto-optical modulation and magnetic measurement.

Magneto-optical heterostructures with second resonance of transverse magneto-optical Kerr effect

Two conventional magneto-plasmonic (MP) structures are firstly superimposed with mirror symmetry to form a symmetric MP heterostructure. These two MP components are separated from each other by a noble metallic layer. The unique feature of this novel heterostructure is that both magneto-plasmon modes of the up and down MP portions can be coupled as the spacer becomes thinner. This intertwining effect leads to appearance of a new peak in the angular transverse magneto-optical Kerr effect (TMOKE) curve of the heterostructure. This new peak which is reported for the first time in the TMOKE signal, is generally similar to plasmon induced transparency (PIT) phenomenon observed in plasmonic multilayered structures. We entitle this novel effect as “second resonance of TMOKE signal”. More importantly, the occurrence angle and magnitude of the second peak can be controlled by varying the thickness and material of separating layer between two MP parts. Also, the dispersion diagram of the heterostructure shows this coupling so that two branches convert into four branches by reducing the thickness of spacer. Furthermore, coupled oscillators model confirms emergence of the second peak in the TMOKE signal. These results can offer great promise for increasing sensitivity of conventional magneto-optical refractive index sensors.

Enhancement in the magneto-optical effect induced by combining multiple modes in a gold film–supported hybrid periodic gold/magnetic nanorod array

In this study, the possibility of enhanced transverse magneto-optical Kerr effect (TMOKE) and performance monitoring of a hybrid nanostructure developed by sandwiching a ferromagnetic film within a gold layer and square periodic nanorod arrays, is theoretically investigated. Based on the findings, the TMOKE signal can be enhanced approximately 33 times when compared to the referenced planar film, which is elucidated by the hybrid of modes in the magnetic film region. In addition, a high level of environmental sensor performance is simultaneously achieved by recording the wavelength resonance positions with the variation of refractive index, which is compatible with gaseous medium from 1 to 1.01, indicating that the structure of the proposal will have applications in environmental monitoring.

Transverse Magneto-Optical Kerr Effect Enhancement in Si–Ni Nanogratings by Mie and Surface Lattice Resonances

Transverse Magneto-Optical Kerr Effect Enhancement in Si–Ni Nanogratings by Mie and Surface Lattice Resonances

Enhanced Sensitivity of Magneto-Optical Surface Plasmon Resonance in the FeCu Superlattices

We demonstrated the sensitivity enhancement for magneto-optical surface plasmon resonance (MOSPR) using noble/ferromagnetic metals multilayers. The proposed structure is based on the Kretschmann configuration in the transverse magneto-optical Kerr effect (TMOKE) methods with the FeCu superlattices (SLs) as magneto-plasmonic materials and gelatin as biomolecules analyte. The dielectric constants of the FeCu SLs are taken from first principles calculation, which is performed by using a full-potential linearized augmented plane wave (FLAPW) method. The important role of the hybridization process in optical transitions has been identified, and it can be modulated by adjusting the thickness of superlattices. The dependence of the reflectivity on the dielectric constant is performed by 4×4 transfer matrix methods. It is found that the minimum reflectivity directly influences the slope of angular spectra, with a maximum slope of TMOKE signal is 12.23/degree. The change in the gelatin’s refractive index results in TMOKE signal response, then the enhancement of the sensitivity of the MOSPR system can be shown.

Strong transverse magneto-optical Kerr effect at normal incidence based on hybrid bound states in the continuum

Strong transverse magneto-optical Kerr effect at normal incidence based on hybrid bound states in the continuum