Magneto-optical Surface Plasmon Resonance Research Articles

Optical fiber sensor based on magneto-optical surface plasmon resonance with ultra-high figure of merit

Abstract Compared to surface plasmon resonance (SPR), the sensors based on the magneto-optical SPR (MOSPR) technique have much higher figure-of-merit (FOM). However, there are no reports about applying MOSPR in the optical fiber structure now. In this work, a novel D-shaped optical fiber sensor based on the MOSPR technique is proposed. The D-shaped optical fiber is coated with a thin silver film and a magneto-optical (MO) material film of Cerium-doped Yttrium-Iron garnet (CeYIG). By applying a magnetic field on the sensing region, the magneto-optical Kerr effect (MOKE) of the CeYIG layer and the related MOSPR phenomenon could be excited when appropriate light is transmitted in the proposed optical fiber sensor. The influence of the structural parameters including the residual cladding thickness, silver and MO material film thicknesses are analyzed theoretically by the finite element method (FEM). With the optimal parameters, the sensor achieves the sensitivity of 5304 nm/RIU. Since the peak width of MOSPR spectra is much narrower than that of the SPR spectra, the FOM of the sensor is largely enhanced to 3864 RIU^(-1) on average and 13260 RIU^(-1) in maximum, which surpasses the optical fiber SPR sensors vastly. The miniaturized and simple design of the D-shaped optical fiber MOSPR sensor, coupled with the ultra-high FOM, offers itself great potential in biochemical sensing applications.

Phthalocyanine and Porphyrin Derivatives and Their Hybrid Materials in Optical Sensors Based on the Phenomenon of Surface Plasmon Resonance

In this review, the state of research over the past fifteen years in the field of the applications of metal phthalocyanines and porphyrin derivatives as well as their hybrid materials with carbon nanotubes, metal oxides, and polymers in optical sensors based on the phenomenon of surface plasmon resonance (SPR) is analyzed. The first chapter of the review presents an analysis of works on the use of porphyrins and phthalocyanines in classical SPR sensors for the detection of gases and volatile organic vapors, as well as their improved modifications, such as total internal reflection ellipsometry (TIRE) and magneto-optical SPR (MOSPR) methods, while the second chapter is devoted to their application for the detection of various analytes in solutions. The third chapter of the review summarizes publications describing recent advances in the use of porous materials based on hybrids of carbon nanotubes and oxides with metal phthalocyanines. The fourth chapter describes two-dimensional metal-organic frameworks (MOFs) based on metal porphyrin derivatives as SPR sensitizers.

High sensitivity magnetic field sensor based on magneto-optical surface plasmon resonance

High sensitivity magnetic field sensor based on magneto-optical surface plasmon resonance

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.

Magnetic Field Sensor Based on Magnetic Optical Surface Plasmon Resonance

Surface plasmon resonance with high sensitivity is widely used in molecular dynamics detection. Herein, a magneto‐optic surface plasmon resonance (MOSPR) sensor based on Au/Co/Au thin film for detecting magnetic fields is developed. The strong coupling between the magneto‐optical waveguide mode and the surface plasmon resonance mode is analyzed and the linear relationship between the reflectivity of the MOSPR sensor and the magnetic field is established. The response, response–recovery time, and dispersion relationship for different magnetic fields are also numerically simulated. Additionally, experimental data on the MOSPR sensor's response to magnetic fields at room temperature (25 °C) are obtained. During the experiment, a differential signal in the light path is applied to reduce the noise generated by the environment. The results demonstrate that the MOSPR sensor exhibits high response, ultrafast response time, and long‐term stability. The study provides a promising approach for detecting magnetic fields with high sensitivity and accuracy.

Enhancement of transverse magneto-optical Kerr effect based on surface plasmon and its application in sensing

In recent years, the combination of magnetic and plasma properties of nanostructures has become a hot research topic. However, most such studies focuse on prism-based sandwich structures, which not only hinders device miniaturization but also has weak transverse magneto-optical Kerr (TMOKE) in amplitude. In this paper, a sub-wavelength periodic nanoporous Au/Co bilayer magneto-optical surface plasmon resonance (MOSPR) sensor is investigated, where the sensing principle is based on the measurement of TMOKE. By optimizing the geometric parameters of the nanostructure, a nearly perfect TMOKE spectrum with a FWHM of only 0.175 nm is obtained, which has a Fano-like pattern and an amplitude close to the theoretical maximum. It is proved that the excitation of high quality SPR enhances the magneto-optical effect. We then analyze the resonant angular shift associated with the TMOKE signal to monitor the change in the analyte refractive index, demonstrating the sensing sensitivity up to 220°RIU−1 and figure of merits (FOM) in excess of 103 in gas. The MOSPR system achieves higher resolution compared to the gold-based SPR system, yielding an order of magnitude higher FOM than the SPR system.

Modeling of Enhanced Polar Magneto-Optic Kerr Effect by Surface Plasmons in Au Bowtie Arrays

The weak magneto-optical (MO) signal of traditional MO materials is indeed an important issue for their further practical applications. Although many strategies have been proposed to improve the MO effect, hybridization with noble metal nanostructures is a promising route in recent years due to the high localized-surface plasmon resonances (LSPR) effect. A new magneto-optical surface plasmon resonance (MOSPR) structure hybrid with Au bowtie arrays is proposed to increase the measuring range of the polar magneto-optical Kerr effect (PMOKE) and the quality factor through the LSPR effect. It is verified by a numerical simulation of the finite element method (FEM). The optimized parameters were found by modulating the shape and geometric dimensions. Owing to the significant LSPR from the Au bowties, a PMOKE amplification signal spectrum with narrow linewidth, and a high amplitude with high-sensing performance was achieved. Compared with the bare magnetic film alone, by optimizing the relevant parameters of the LSPR structure, the maximum signal increases 3255 times, and the quality factor can be greatly improved, which would provide important guidance and help for the practical application of MO devices.

Magneto-optic surface plasmon resonance properties of core-shell Fe3O4@Ag nanoparticles

The magneto-optic surface plasmon resonance (MOSPR) properties of core-shell Fe3O4@Ag nanoparticles (NPs) were successfully investigated using the Kretschmann configuration. The four layer configuration system consists of prism/Au/Fe3O4@Ag/air. At the plasmon resonance frequency, a prominent resonant enhancement of magneto-optical activity was observed. An external magnetic field of 40, 50 and 60 Oe was applied in the longitudinal, polar, and transversal configurations with variation in the positive and negative directions in the longitudinal configuration. In the longitudinal configuration, the SPR angle shifted to the larger and lower angles when an external magnetic field was applied in the positive and negative directions, respectively. Under an external magnetic field, the SPR angle shifted to the larger angle for polar and transversal configurations. The non-reciprocal reflection of light was exploited under an external magnetic field applied to core-shell Fe3O4@Ag magnetic NPs. The SPR angle shift is observed in each configuration. The results indicated that the MOSPR system might be used for next generation of biosensor application.

Enhancement of transverse magneto-optical Kerr effects and high sensing performance in a trilayer structure with nanopore arrays

The transverse magneto-optical Kerr effects (T-MOKEs) and sensing performance in a magneto-optical surface plasmon resonance (MOSPR) structure comprising a nanoporous gold/Co6Ag94 bilayer with a square-subwavelength period on a gold slab are theoretically investigated. Benefiting from the excitation of the surface plasmon resonance by optimizing the related parameters of the proposed MOSPR structure, we obtain a magnified T-MOKE signal with a high sensing performance in a gas environment. In this system, a sharp Fano-like T-MOKE spectrum with a narrow linewidth and a high amplitude is achieved. This strategy is important for obtaining new classes of detectors for monitoring air quality.

MagnetoPlasmonic Waves/HOMO-LUMO Free π-Electron Transitions Coupling in Organic Macrocycles and Their Effect in Sensing Applications

Optical and magneto-optical surface plasmon resonance (MOSPR) characterization and preliminary sensing test onto single- and multi-layers of two organic macrocycles have been performed; TbPc2(OC11H21)8 phthalocyanine and CoCoPo2 porphyrin were deposited by the Langmuir-Schäfer (LS) technique onto proper Au/Co/Au magneto-optical transducers. Investigations of the MOSPR properties in Kretschmann configuration by angular modulation, gives us an indication about the potential discrimination of two organic macrocycles with absorption electronic transition in and out of the propagating plasmon energy spectral range. An improved molecular vapors sensitivity increase by the MOSPR sensing probe can be demonstrated depending on the overlap between the plasmonic probe energy and the absorption electronic transitions of the macrocycles under investigation. If the interaction between the plasmon energy and molecular HOMO-LUMO transition is preserved, a variation in the complex refractive index takes place. Under this condition, the magneto-plasmonic effect reported as 1/|MOSPR| signal allows us to increase the detection of molecules deposited onto the plasmonic transducer and their gas sensing capacity. The detection mechanism appears strongly enhanced if the Plasmon Wave/HOMO-LUMO transitions energy are in resonance. Under coupling conditions, a different volatile organic compounds (VOC) sensing capability has been demonstrated using n-butylamine as the trial molecule.

Surface plasmon resonances boost the transverse magneto-optical Kerr effect in a CoFeB slab covered by a subwavelength gold grating for highly sensitive detectors.

Herein, we have theoretically investigated the sensing performance-including enormous increase in the sensitivity and figure of merit (FOM)-of a magneto-optical surface plasmon resonance (MOSPR) sensor, which is based on the transverse magneto-optical Kerr effect (T-MOKE) in a ferromagnet coupled with a noble-metal grating. Specifically, we propose to use a CoFeB magnetic slab covered by a subwavelength, periodic gold grating configured as a magnetoplasmonic heterostructure. In such a device, sharp, Fano-like T-MOKE signals of high amplitude can be achieved due to the surface plasmon resonances (SPRs) excited in the presence of the gold grating, especially after optimizing the grating period. Tiny changes in the refractive index of an analyte surrounding the MOSPR sensor can be measured by analyzing the shift in the angle of incidence of the resonance positions of the T-MOKE signals. By calculating these resonance positions, we have demonstrated that it is possible to achieve a considerable sensitivity of 105° RIU-1 and a FOM as high as ∼102. Such a MOSPR sensing system can be exploited in biosensors with high detection limits.

Magneto-Optic-Plasmonic Sensors With Improved Performance

In this article, a novel magneto-optic-plasmonic (MOP) surface plasmon resonance (SPR) effect-based sensor configuration using a conventional mutlilayer combination of metal and dielectrics is proposed, and its performance: sensitivity and detection limit of the proposed magneto-optic SPR (MOSPR) sensor (at the magnetic field, H = ±H) with the conventional SPR sensor (at H = 0) at the excitation wavelength, λ = 632.8 and 785 nm in air and helium is compared. Both the sensitivity and detection limit of the optimized MOSPR sensor showed significantly larger values over the sensitivity and detection limit of the SPR sensor, almost 4× the performance of these sensors.

A refractive index sensor based on magneto-optical surface plasmon resonance

Abstract A refractive index sensor based on magneto-optical surface plasmon resonance (MOSPR) is proposed. The device is made up of a prism coupling system consists of prism/TiN/SiO2/YIG/CeYIG/Au/liquid. System simulation is performed by 4 × 4 transfer matrix method. It is found that the structure has excellent sensing performance. Magnetron sputtering vacuum coating method is used to fabricate the dielectric film of the sample, and a MOSPR sensor detection platform is built to test the concentration of 0–30% alcohol solution. As the concentration of the alcohol solution increases, the refractive index of the sensing liquid increases and transverse Kerr effect is enhanced. Meanwhile the incident angle corresponds to the maximum value of the MOSPR curve (the difference of reflectance with opposite magnetic fields) also increases with the alcohol concentration. This structure of MOSPR is expected to be applied in the field of micro-measurement and biochemical sensing.

Surface Plasmon Resonance (SPR) to Magneto-Optic SPR

In this editorial, a brief background of the surface plasmon resonance (SPR) principle is discussed, followed by several aspects of magneto-optic SPR (MOSPR) and sensing schemes from the viewpoint of fundamental studies and potential technological applications. New sensitivity metrics are introduced that would allow researchers to compare the performance of SPR and MOSPR-based sensors. Merits of MOSPR over SPR based sensors and challenges faced by MOSPR sensors in terms of their practical use and portability are also considered. The editorial ends with potential new configurations and future prospects. This work is considered highly significant to device engineers, graduate and undergraduate students, and researchers of all levels involved in developing new classes of bio-devices for sensing, imaging, environmental monitoring, toxic gas detection, and surveying applications to name a few.

Microstructure, Surface Plasmon, Magneto-Optic Surface Plasmon, and Sensitivity Properties of Magneto-Plasmonic Co/Au Multilayers

Microstructure properties of Co/Au multilayers prepared using dc-magnetron sputtering is reported using X-ray reflectivity (XRR) and X-ray diffraction (XRD) analysis. XRR profiles of these multilayers showed excellent bilayer periodicity. The XRD spectra displayed Co layer thickness-dependent properties. However, annealing increased lateral tensile strain decreased compressive strain along the normal substrate direction. While surface roughness, crystallite grain size, and strain are affected by Co layer thickness, microstructure and periodicity are dominated by fcc-Au (111). Surface plasmon resonance (SPR) and magneto-optic SPR study of an optimized Co/Au multilayer in Kretschmann configuration for air-He and water-Methanol media showed an enhanced sensitivity by over 4 times when excited at the wavelength of 785 nm as compared to the conventional SPR configuration when excited at the wavelength of 632.8 nm. This enhancement in MOSPR sensitivity means the detection limit of this class of transducers can be substantially improved by tuning Co/Au layer thickness, wavelength, and incident angle of optical radiation.

Magneto-Optic Surface Plasmon Resonance Ti/Au/Co/Au/Pc Configuration and Sensitivity

Magneto-optic surface plasmon resonance (MOSPR)-based sensors are highly attractive as next-generation biosensors. However, these sensors suffer from oxidation leading to degradation of performance, reproducibility of the sensor surface, because of the difficulty of removing adsorbed materials, and degradation of the sensor surface during surface cleaning and these limit their applications. In this paper, I propose MOSPR-based biosensors with 0 to 15 nm thick inert polycarbonate laminate plastic as a protective layer and theoretically demonstrate the practicability of my approach in water-medium for three different probing samples: ethanol, propanol, and pentanol. I also investigate microstructure and magnetic properties. The chemical composition and layered information of the sensor are investigated using X-ray reflectivity and X-ray diffraction analyses and these show distinct face-centered-cubic (fcc)-Au (111) phases, as dominated by the higher density of conduction electrons in Au as compared to Co. The magnetic characterization measured with the in-plane magnetic field to the sensor surface for both the as-deposited and annealed multilayers showed isotropic easy axis magnetization parallel to the multilayer interface at a saturating magnetic field of <100 Oersted (Oe). The sensor showed a maximum sensitivity of 5.5 × 104%/RIU (refractive index unit) for water–ethanol media and the highest detection level of 2.5 × 10−6 for water-pentanol media as the protective layer is increased from 0 to 15 nm.

Microstructure and magneto-optical surface plasmon resonance of Co/Au multilayers

Magneto-optical surface plasmon resonance (MOSPR) sensors benefit from a magneto-optic enhancement with respect to surface plasmon resonance (SPR) sensors, making these devices attractive for biosensing applications. Typical design compromises seek to balance magneto-optic effects and optical losses associated with surface plasmon waves extending to the ferromagnetic layer. Here, we demonstrate that Co/Au multilayers can yield sizeable MOSPR improvements in spite of the relative high total Co layer thickness. Co (tCo)/Au (2 nm) multilayers, with 1.2 ≤ tCo ≤ 1.8 nm are prepared and characterized. X-ray analysis shows that the microstructure maintains high layer periodicity and improves upon annealing. The multilayer structures were then modeled to study their SPR/MOSPR sensitivities, suggesting that the MOSPR sensitivity is enhanced by a factor of up to 3 and 4 with respect to the SPR sensitivity when the devices are operated in Air and Water media, respectively. We find that multilayers provide a particular advantage when operating the sensors in Water-based media.

Highly sensitive sensors of fluid detection based on magneto-optical optical Tamm state

We propose a new magneto-optical optical Tamm state (MOOTS) sensor in fluid detection. The device consists of a dielectric magneto-optical thin film of Ce-doped Y3Fe5O12 (CeYIG), a metallic film of Ag and a periods of the distributed Bragg reflector (DBR). Finite element method (FEM) and 4 × 4 transfer matrix method are employed to calculate the figure of merit (FOM) of sensitivity. Calculation results indicate that a FOM of 1224.21/RIU for gas refractive index variation from 1.0000 to 1.0006 can be obtained when the incident wavelength is 1064 nm, which is much larger than the FOM of magneto-optical surface plasmon resonance (MOSPR) device. Meanwhile, our MOOTS sensor is insusceptible to the influence of smoothness of the interface of deposited layers and can provide the great error tolerance, which is more conducive to the manufacture, production and actual performance. In addition, the experiment route to detect the refractive index of air and NaCl solution has been revealed.

Characterization of Au/Fe/Au and Au/Co/Au Magneto-Plasmonic Multilayers as an Ethanol Vapor Sensor

In this paper, we investigate the sensing performance of Au/Fe/Au and Au/Co/Au magneto-plasmonic nanostructures as transducers as well as the performance of TiO2 thin film and TiO2 NPs as sensing layers. A comparison between sensing performance of the traditional surface plasmon resonance (SPR) and the magneto-optic (MO) SPR (MOSPR) transducing techniques is presented here. The surface plasmon wave vector in these transducers which are consisted of metallic and magnetic materials is modulated by external magnetic field in the transverse configuration. Magneto-plasmonic structures show a great enhancement of an MO Kerr effect when the SPR condition is satisfied. As such enhancement strongly depends on the excitation conditions of the surface plasmon polariton (SPP) and, therefore, on the refractive index of the dielectric in contact with the metal layer, we use this enhanced MO signal as the sensing magnitude for investigating molecular interactions between ethanol vapor and TiO2 nanostructures onto the transducers. Besides, when the SPP is excited, applied magnetic field would modulate the SPP wave vector. The modulated nature of MOSPR signal would lead to a higher sensing performance in terms of sensitivity and signal-to-noise ratio with respect to the traditional SPR signal. Moreover, our results show that using TiO2 NPs in the vicinity of multilayer transducers creates a better sensing performance which is caused by porosity and enhancement in the surface area of absorbent layer.

Magneto-plasmonic sensor with one dimensional photonic crystal for methane detection

In this paper we present a highly sensitive magneto-optical surface plasmon resonance (MOSPR) sensor based on Ce1Y2Fe5O12 (Ce:YIG), noble metal (Gold) and one dimensional photonic crystal (1D-PC) for methane detection. We find that due to a combination of strong magneto-optical effect of Ce:YIG and ultralong surface plasmon propagation caused by one dimensional photonic crystal, sensitivity of the sensor to the methane concentration variation achieve a maximum value of 178.2/1%. These results indicate a great potential for application of the structure in methane detection.