Magnetic modulation of Fano resonances in optically thin terahertz superlattice metasurfaces

2021 ◽  
Author(s):  
Subhajit Karmakar ◽  
Ravi Varshney ◽  
Dibakar Roy Chowdhury
Keyword(s):  
Magnetic Field ◽  
Free Space ◽  
Skin Depth ◽  
Electromagnetic Energy ◽  
Magnetic Control ◽  
Fano Resonances ◽  
Electromagnetic Responses ◽  
On Chip ◽  
Magneto Resistance ◽  
Sub Wavelength

Abstract Optically thin metasurfaces operating at sub-skin depth thicknesses are intriguing because of its associated low plasmonic losses (compared to optically thick, beyond skin-depth metasurfaces). However, their applicability has been restricted largely because of reduced free space coupling with incident radiations resulting in limited electromagnetic responses. To overcome such limitations, we propose enhancement of effective responses (resonances) in sub-skin depth metasurfaces through incorporation of magneto-transport (Giant Magneto Resistance, GMR) concept. Here, we experimentally demonstrate dynamic magnetic modulation of structurally asymmetric metasurfaces (consisting of superlattice arrangement of thin (~ 10 nm each) magnetic (Ni)/ nonmagnetic (Al) layers) operating at terahertz (THz) domain. With increasing magnetic field (applied from 0 to 30 mT approximately, implies increasing superlattice conductivity), we observe stronger confinement of electromagnetic energy at the resonances (both in dipole and Fano modes). Therefore, this study introduces unique magnetically reconfigurable ability in Fano resonant THz metamaterials, which directly improves its performances operating in the sub-skin depth regime. Our study can be explained by spin-dependent terahertz magneto-transport phenomena in metals and can stimulate the paradigm for on-chip spin-based photonic technology enabling dynamic magnetic control over compact, sub-wavelength, sub-skin depth metadevices.

scholarly journals A Plasmonic Chip-Scale Refractive Index Sensor Design Based on Multiple Fano Resonances

Sensors ◽  
2018 ◽  
Vol 18 (10) ◽  
pp. 3181 ◽  
Author(s):  
Kunhua Wen ◽  
Li Chen ◽  
Jinyun Zhou ◽  
Liang Lei ◽  
Yihong Fang
Keyword(s):  
Refractive Index ◽  
Fdtd Method ◽  
High Sensitivity ◽  
Refractive Index Sensor ◽  
Fano Resonances ◽  
Metal Insulator Metal ◽  
High Figure ◽  
On Chip ◽  
Difference Time ◽  
Sub Wavelength

In this paper, multiple Fano resonances preferred in the refractive index sensing area are achieved based on sub-wavelength metal-insulator-metal (MIM) waveguides. Two slot cavities, which are placed between or above the MIM waveguides, can support the bright modes or the dark modes, respectively. Owing to the mode interferences, dual Fano resonances with obvious asymmetrical spectral responses are achieved. High sensitivity and high figure of merit are investigated by using the finite-difference time-domain (FDTD) method. In view of the development of chip-scale integrated photonics, two extra slot cavities are successively added to the structure, and consequently, three and four ultra-sharp Fano peaks with considerable performances are obtained, respectively. It is believed that this proposed structure can find important applications in the on-chip optical sensing and optical communication areas.

Thin-skin electromagnetic fields in the neighbourhood of surface-breaking cracks in metals

1991 ◽  
Vol 434 (1892) ◽  
pp. 587-603 ◽  
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Field ◽  
Free Space ◽  
Skin Depth ◽  
Rectangular Slot ◽  
Numerical Predictions ◽  
First Case ◽  
Wide Range ◽  
Thin Skin ◽  
The Magnetic Field

Electromagnetic non-destructive evaluation techniques are widely used to detect and size surface-breaking cracks in metal structures and components. The precise distribution of the electromagnetic field around such a crack depends on the frequency of the applied field, the material properties of the metal and the crack geometry. In many situations, the skin depth of the electromagnetic field in the metal is small compared with the crack dimensions. If this is the case, the crucial parameter that determines the way the electromagnetic field in air couples to the field in the metal is m = μ 0 l / μδ , where μ and μ 0 are the metal and free space permeabilities respectively and l / δ is the ratio of the crack length scale l to the skin depth δ . If the metal is ferromagnetic, m can take a wide range of values and the distribution of the electromagnetic field around the crack is very different in the two limiting cases m = 0 and m ≫ 1. In the first case, the magnetic flux emerging from the crack is directed into the metal surface whereas in the second case, the flux is directed into free space. In this work, the distribution of the electromagnetic field around a surface-breaking crack is determined for arbitrary values of m . The theory is developed for cracks of general shape and numerical calculations of the free-space components of the magnetic field are made for rectangular and semi-elliptical shaped cracks. The numerical predictions are found to be in good agreement with experimental measurements of the magnetic field above a rectangular slot, cut in a flat plate of mild steel.

scholarly journals Fano resonances in transport across a quantum well in a tilted magnetic field

1995 ◽  
Vol 51 (23) ◽  
pp. 17219-17222 ◽  
Author(s):  
Jens U. Nöckel ◽  
A. Douglas Stone
Keyword(s):  
Magnetic Field ◽  
Quantum Well ◽  
Fano Resonances ◽  
Tilted Magnetic Field

Frequency Tuning of a Nonlinear Electromagnetic Energy Harvester

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Longhan Xie ◽  
Ruxu Du
Keyword(s):  
Magnetic Field ◽  
Permanent Magnets ◽  
Energy Harvester ◽  
Frequency Tuning ◽  
Nonlinear Behavior ◽  
Stretch Ratio ◽  
Electromagnetic Energy ◽  
Elastic Strings ◽  
Simulation And Experiment ◽  
Frequency Tunable

This paper investigates a frequency-tunable nonlinear electromagnetic energy harvester. The electromagnetic harvester mainly consists of permanent magnets supported on the base to provide a magnetic field, and electrical coils suspended by four even-distributed elastic strings to be an oscillating object. When the base provides external excitation, the electrical coils oscillate in the magnetic field to produce electricity. The stretch length of the elastic strings can be tuned to change their stretch ratio by tuning adjustable screws, which can result in a shift of natural frequency of the harvester system. The transverse force of the elastic strings has nonlinear behavior, which broadens the system's frequency response to improve the performance of the energy harvester. Both simulation and experiment show that the above-discussed electromagnetic energy harvester has nonlinear behavior and frequency-tunable ability, which can be used to improve the effectiveness of energy harvesting.

scholarly journals Direct quantification of topological protection in symmetry-protected photonic edge states at telecom wavelengths

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Sonakshi Arora ◽  
Thomas Bauer ◽  
René Barczyk ◽  
Ewold Verhagen ◽  
L. Kuipers
Keyword(s):  
Near Field ◽  
Edge States ◽  
Quantum Networks ◽  
Hall Effects ◽  
Upper Limits ◽  
On Chip ◽  
Symmetry Protected ◽  
Topological Robustness ◽  
Direct Quantification ◽  
Sub Wavelength

AbstractTopological on-chip photonics based on tailored photonic crystals (PhCs) that emulate quantum valley-Hall effects has recently gained widespread interest owing to its promise of robust unidirectional transport of classical and quantum information. We present a direct quantitative evaluation of topological photonic edge eigenstates and their transport properties in the telecom wavelength range using phase-resolved near-field optical microscopy. Experimentally visualizing the detailed sub-wavelength structure of these modes propagating along the interface between two topologically non-trivial mirror-symmetric lattices allows us to map their dispersion relation and differentiate between the contributions of several higher-order Bloch harmonics. Selective probing of forward- and backward-propagating modes as defined by their phase velocities enables direct quantification of topological robustness. Studying near-field propagation in controlled defects allows us to extract upper limits of topological protection in on-chip photonic systems in comparison with conventional PhC waveguides. We find that protected edge states are two orders of magnitude more robust than modes of conventional PhC waveguides. This direct experimental quantification of topological robustness comprises a crucial step toward the application of topologically protected guiding in integrated photonics, allowing for unprecedented error-free photonic quantum networks.

scholarly journals Controlling Refraction Using Sub-Wavelength Resonators

2018 ◽  
Vol 8 (10) ◽  
pp. 1942
Author(s):  
Yue Chen ◽  
Robert Lipton
Keyword(s):  
Frequency Dependence ◽  
Free Space ◽  
Near Infrared ◽  
Center Frequency ◽  
Negative Index ◽  
Index Properties ◽  
Frequency Bands ◽  
Transmitted Signal ◽  
Sub Wavelength

We construct metamaterials from sub-wavelength nonmagnetic resonators and consider the refraction of incoming signals traveling from free space into the metamaterial. We show that the direction of the transmitted signal is a function of its center frequency and bandwidth. The directionality of the transmitted signal and its frequency dependence is shown to be explicitly controlled by sub-wavelength resonances that can be calculated from the geometry of the sub-wavelength scatters. We outline how to construct a medium with both positive and negative index properties across different frequency bands in the near infrared and optical regime.

scholarly journals On annihilation of the relativistic electron vortex pair in collisionless plasmas

2018 ◽  
Vol 84 (6) ◽  
Author(s):  
K. V. Lezhnin ◽  
F. F. Kamenets ◽  
T. Zh. Esirkepov ◽  
S. V. Bulanov
Keyword(s):  
Magnetic Field ◽  
Collisionless Plasma ◽  
Vortex Formation ◽  
Vortex Pair ◽  
Skin Depth ◽  
Secondary Vortex ◽  
Vortex System ◽  
Collisionless Plasmas ◽  
Secondary Vortices ◽  
The Magnetic Field

In contrast to hydrodynamic vortices, vortices in a plasma contain an electric current circulating around the centre of the vortex, which generates a magnetic field localized inside. Using computer simulations, we demonstrate that the magnetic field associated with the vortex gives rise to a mechanism of dissipation of the vortex pair in a collisionless plasma, leading to fast annihilation of the magnetic field with its energy transforming into the energy of fast electrons, secondary vortices and plasma waves. Two major contributors to the energy damping of a double vortex system, namely, magnetic field annihilation and secondary vortex formation, are regulated by the size of the vortex with respect to the electron skin depth, which scales with the electron$\unicode[STIX]{x1D6FE}$factor,$\unicode[STIX]{x1D6FE}_{e}$, as$R/d_{e}\propto \unicode[STIX]{x1D6FE}_{e}^{1/2}$. Magnetic field annihilation appears to be dominant in mildly relativistic vortices, while for the ultrarelativistic case, secondary vortex formation is the main channel for damping of the initial double vortex system.

The theory of the magneto-resistance effects in polar semi-conductors

1955 ◽  
Vol 227 (1169) ◽  
pp. 241-251 ◽  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Hall Coefficient ◽  
Low Temperatures ◽  
Magneto Resistance

General expressions are obtained for the Hall coefficient and transverse magneto-resistance effect in polar semi-conductors, and the variation of these effects with temperature, magnetic field strength and degeneracy of the electrons is discussed. At low temperatures the magneto-resistance effect may become very large, contrary to the prediction of the freepath theory.

scholarly journals Sparsity-based continuous wave terahertz lens-free on-chip holography with sub-wavelength resolution

2019 ◽  
Vol 27 (2) ◽  
pp. 702 ◽  
Author(s):  
Zeyu Li ◽  
Qiang Yan ◽  
Yu Qin ◽  
Weipeng Kong ◽  
Guangbin Li ◽  
...  
Keyword(s):  
Continuous Wave ◽  
Wavelength Resolution ◽  
On Chip ◽  
Sub Wavelength

Evaluation of the Equivalent Lumped Element Parameters of Modified Microstrip Ring Resonator

2015 ◽  
Vol 735 ◽  
pp. 278-281
Author(s):  
Yi Lung Then ◽  
Kok Yeow You ◽  
Mohamad Ngasri Dimon ◽  
Wei Ying Lai
Keyword(s):  
Magnetic Field ◽  
Free Space ◽  
Ring Resonator ◽  
Element Model ◽  
Network Analyzer ◽  
Simulation Data ◽  
Lumped Element ◽  
Lumped Element Model ◽  
Microstrip Ring ◽  
Microstrip Ring Resonator

Microstrip ring resonator (MRR) sensor was modeled by simple equivalent lumped element circuits in free space based on simulation data obtained from Microwave Office (AWR) simulator and comparison was made with the measurements using the E5071C Network Analyzer. The calculated reflection coefficient, |G| and complex input impedanceZinusing lumped element model were compared with the measurements results. Both results showed well agreement with a little discrepancy, basically due to imperfect soldering. The MRR was designed to have operating frequencies between 0.5 GHz and 4.5 GHz. The maximum surrounding of magnetic field,Hϕis within 15 A/m in free space.

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