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Spin Textures as Sources for Magnons with Short Wavelengths and 3D Mode Profiles
Published in Gianluca Gubbiotti, Three-Dimensional Magnonics, 2019
The second prominent mechanism for converting uniform external magnetic fields into finite-wavelength spin waves relies on Fano resonances [30]. In general a Fano resonance describes the situation where a discrete resonance is interacting with a continuous dynamic mode. In terms of magnonics this could be a situation where the external field excites a discrete local magnetic resonance of the sample, which then hybridizes with the continuous spin-wave dispersion relation, causing spin-wave excitation. An example for Fano resonance spin-wave excitation is schematically shown in Fig. 8.3b. The external field excites the precessional eigenfrequency of a ferromagnetic wire on top of a ferromagnetic film. The dynamic dipolar fields from this precession in turn interact with the film, locally exciting spin waves [4]. The so-called magnonic grating coupler is another example for a Fano resonance [101, 102].
Graded Magnonic Index and Spin Wave Fano Resonances in Magnetic Structures: Excite, Direct, Capture
Published in Sergej O. Demokritov, Spin Wave Confinement, 2017
V.V. Kruglyak, C. S. Davies, Y. Au, F. B. Mushenok, G. Hrkac, N. J. Whitehead, S. A. R. Horsley, T. G. Philbin, V. D. Poimanov, R. Dost, D. A. Allwood, B. J. Inkson, A. N. Kuchko
In the most basic case, the FMR frequency of magnetic samples depends on the saturation magnetization of the material, the sample’s dimensions and the applied bias magnetic field. The same is true for spin wave (higher-order) resonances. It is possible to design a system of two neighboring (or connecting) magnetic elements that have different dominant resonance frequencies for a given bias magnetic field value/orientation. When the entire system is pumped by a harmonic microwave magnetic field at the higher resonance frequency, the resonance is excited in one element only (the “transducer”). The coupling between the magnetizations of the two elements then leads to injection of spin waves into the second element (the “waveguide”), with their wavelength dictated by the magnonic dispersion in the waveguide. Such a resonance, in which the energy from one resonantly excited element with a discrete spectrum is “leaked” into wave modes propagating in the element with a continuous spectrum, is an example of a Fano resonance [37,38].
Basics of Resonance
Published in Banshi Dhar Gupta, Anand Mohan Shrivastav, Sruthi Prasood Usha, Optical Sensors for Biomedical Diagnostics and Environmental Monitoring, 2017
Banshi Dhar Gupta, Anand Mohan Shrivastav, Sruthi Prasood Usha
Fano resonance is a resonant-scattering process, where the superimposition of two scattering amplitudes occurs. One is due to the bulk/background process and the other due to the excitation of the resonance phenomenon. The combination of fano resonance with SPR to realize optical sensors for practical applications enhances the sensitivity of the sensor by around 2000 times in comparison to simple SPR configuration. The arrangement is shown in Figure 2.16. It is similar to the Kretschmann configuration. In this arrangement, the base of the prism is coated with a metal layer followed by a coupling layer (of suitable dielectric constant) that can support the generation of SPs at the metal–coupling layer interface. Over the coupling layer, a guiding layer is introduced which can be treated as a planar waveguide and is surrounded by the sensing medium. The light incident on the prism–metal interface generates evanescent wave whose field decays exponentially in to the metal layer to excite SP wave. The generated SP–evanescent field tail can excite planar waveguide mode. This planar waveguide mode is followed by an evanescent field in the coupling layer and sensing layer. The generation of evanescent fields in the coupling layer due to planar waveguide mode and SP mode results in a coupling between them. The degree of coupling and hence the sensor performance can be controlled by optimizing the thickness and the RI of the coupling and guiding layers. Using the Kretschmann configuration, a coupling between the SP mode and planar waveguide mode can be achieved to generate a hybrid mode. The reflectance spectrum at the output shows the appearance of sharp fano resonance in the SPR curve (Zheng et al. 2017).
Plasmonic Grating-Based Refractive Index Sensor with High Sensitivity
Published in IETE Journal of Research, 2023
Hardik Mathuriya, Rukhsar Zafar, Ghanshyam Singh
This paper also presents a Plasmonic grating-based sensor in which Fano resonance is excited. A defect region is deliberately set up in the grating. This defect region efficiently acts as a bright mode and it is directly excited with the input signal. When a nano-metallic slit is introduced in the defect region, it changes the resonance condition according to the interference between super-radiant or bright mode and sub-radiant or dark mode. The interference between these two modes causes an asymmetrical resonance profile to emerge Fano resonance. It is quite different from traditional resonance [15–20]. Due to the intriguing property of Fano profile, the suggested device is quite viable in bio-sensing and chemical sensing. The performance evaluation of the sensor is done using sensitivity, Quality factor, and FOM. Our results indicate that performance quantifying parameters can be varied with changes in the geometrical parameters of the proposed device. The proposed sensor offers a small footprint of 10×1.2 μm2. The detailed structural geometry is discussed in Section 2. Results and Discussions section is presented in Section 3, while Section 4 presents the application of proposed device in sensing principle.
Transformation of twin-peak electromagnetically induced transparency to twin-peak electromagnetically induced absorption based on magnetic dipole and dielectric resonator
Published in Waves in Random and Complex Media, 2023
Yu-jing Yin, You Lv, Didi Zhu, Hai-Feng Zhang
The appearance of the right EIT window is owning to the resonance generated by VR and SR, which can be regarded as the role of an all-medium resonator. The two upper resonators are both excited to form a strong displacement current, which can be regarded as the electric dipole, then VR and SR resonating for the interaction of the displacement current. The displacement current of VR is relatively weaker compared with SR, for the larger size will reduce the coupling strength with incident plane waves. During the coupling, the direction of the displacement current of VR is reversed, leading to the electric displacement of the two resonators turning opposite in orientation. Then, VR and SR perform weak hybrid coupling, with the weakening of the surrounding electric field of the SR, causing the emergence of the EIT window. Besides, Fano resonance is the coupling effect arising from the interaction between narrow discrete states (dark modes) and broad continuous states (bright modes) [55–57]. EIT can also be originally deemed as the Fano resonance under certain conditions [58,59]. However, the phase mutation displayed later, the coupling analysis of three bright modes and atlas of the time domain can prove the EIT phenomenon in this work.
Applications and challenges of elemental sulfur, nanosulfur, polymeric sulfur, sulfur composites, and plasmonic nanostructures
Published in Critical Reviews in Environmental Science and Technology, 2019
Yong Teng, Qixing Zhou, Peng Gao
The asymmetric Fano resonances arise from the interference between two or more oscillators and have been found in plasmonic nanoparticles, photonic crystals, and electromagnetic metamaterials (Yanchuk et al., 2010). The autoionization of atoms and the asymmetric shape of these resonances was firstly explained by Fano (Gallinet & Martin, 2011). Especially, for the Fano resonances in plasmonic nanostructures and metamaterials, an ab initio theory is developed using the Feshbach formalism to reveal the role played by the electromagnetic modes and material losses in the system, and engineer Fano resonances in arbitrary geometries (Gallinet & Martin, 2011). Fano resonances, produced by the interference between bright (superradiant) and dark (subradiant) modes of the nanoparticle cluster, and produce extinction features with characteristic narrow and asymmetric line shapes, that enables the applications in plasmonic rulers, biosensors, etc. (Yanchuk et al., 2010; Lovera et al., 2013; Francescato, Giannini, & Maier, 2012). They are inherently sensitive to changes in geometry or the local dielectric environment, thus permits a highly sensitive tenability of the Fano dip in both wavelength and amplitude by varying cluster dimensions, geometry, and relative size of the individual nanocluster components (Lassiter et al.,2010).