scholarly journals Effective medium concept in temporal metamaterials

Nanophotonics ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 379-391 ◽  
Author(s):  
Victor Pacheco-Peña ◽  
Nader Engheta
Keyword(s):  
Scientific Community ◽  
Effective Permittivity ◽  
Step Function ◽  
Effective Medium ◽  
Electromagnetic Response ◽  
Multilayered Structures ◽  
Filling Fraction ◽  
Time Harmonic ◽  
Matter Interaction ◽  
Materials Used

AbstractMetamaterials are mostly designed in the time-harmonic scenario where wave propagation can be spatially manipulated. Tailoring the electromagnetic response of media in time has also gained the attention of the scientific community in order to achieve further control on wave-matter interaction both in space and time. In the present work, a temporally effective medium concept in metamaterial is theoretically investigated as a mechanism to create a medium with a desired effective permittivity. Similar to spatially subwavelength multilayered metamaterials, the proposed “temporal multilayered”, or “multistepped” metamaterial, is designed by alternating in time the permittivity of the medium between two values. In so doing, the temporally periodic medium can be modeled as an effective metamaterial in time with an effective permittivity initiated by a step function. The analogy between the temporal multistepped and the spatial multilayered metamaterials is presented demonstrating the duality between both domains. The proposed temporal metamaterial is analytically and numerically evaluated showing an excellent agreement with the designed parameters. Moreover, it is shown how the effective permittivity can be arbitrarily tailored by changing the duty cycle of the periodic temporal metamaterial. This performance is also connected to the spatial multilayer scenario in terms of the filling fraction of the different materials used to create the multilayered structures.

Tribological Aspects of AlN-TiN Thin Composite Films

2004 ◽  
Vol 843 ◽  
Author(s):  
C. Waters ◽  
G. Young ◽  
S. Yarmolenko ◽  
X. Wang ◽  
J. Sankar
Keyword(s):  
Fracture Toughness ◽  
Critical Load ◽  
Composite Films ◽  
Scratch Test ◽  
Small Scale ◽  
Wear Properties ◽  
Multilayered Structures ◽  
Tin Film ◽  
Materials Used ◽  
Increasing Load

AbstractPhysical properties, and the friction and wear are important issues in small-scale applications, it is therefore essential that the materials used have good micromechanical and tribological properties. The adhesion, fracture toughness and wear properties of AlN-TiN thin composite films is being investigated in this study. The multilayered structures are generated using Pulsed Laser Deposition (PLD). The durability and functionality of thin films is subject to the adhesion between the coating and the underlying substrate in addition to it's resistance to cracking. The magnitude of the critical load during a scratch test is related to the adhesion of the substrate to the coating. In this test a Berkovich indenter is used for measurements and is drawn across the surface of a coating under an increasing load. The magnitude of the critical load will be studied for various films from a monolayer TiN film to different AlN-TiN films and those relative results compared to their facture toughness and their wear properties. Despite the adhesion, the critical load depends on several other parameters including the friction coefficient. The critical characteristic load is shown to depend on the number of layers and the relative AlN-TiN thickness. The fracture toughness showed a weak dependence on the layer characteristics.

Microwave Metamaterials Containing Magnetically Soft Microwires

2010 ◽  
Vol 75 ◽  
pp. 224-229 ◽  
Author(s):  
Mihail Ipatov ◽  
V. Zhukova ◽  
Arcady P. Zhukov ◽  
Larissa V. Panina
Keyword(s):  
Magnetic Properties ◽  
Effective Permittivity ◽  
Microwave Frequency ◽  
Index Of Refraction ◽  
Electromagnetic Response ◽  
Transmission Spectra ◽  
Mechanical Stimuli ◽  
Metallic Wire ◽  
Negative Index Of Refraction ◽  
Wire Media

In this paper we discuss the development of metamaterials containing ferromagnetic microwires which makes it possible to tune the electromagnetic response in the microwave frequency band. Metallic wire media are known to demonstrate very strong dispersion of the effective permittivity at GHz frequencies. At certain conditions, the magnetic properties of constituent wires may strongly contribute to the system losses owing to the magnetoimpedance effect, resulting in unusual dependence of the permittivity on the external magnetic or mechanical stimuli. We also demonstrate the possibility to design the wire media with a negative index of refraction utilizing natural magnetic properties of wires. The results involve theoretical modeling and measurements of the reflection/transmission spectra by free-space methods. A reasonable agreement between theoretical and experimental data is demonstrated.

scholarly journals Analogies between optical propagation and heat diffusion: applications to microcavities, gratings and cloaks

2015 ◽  
Vol 471 (2183) ◽  
pp. 20150143 ◽  
Author(s):  
C. Amra ◽  
D. Petiteau ◽  
M. Zerrad ◽  
S. Guenneau ◽  
G. Soriano ◽  
...  
Keyword(s):  
Heat Conduction ◽  
Diffraction Gratings ◽  
Anisotropic Media ◽  
Thermal Parameters ◽  
Heat Diffusion ◽  
Transformation Optics ◽  
Multilayered Structures ◽  
Optical Propagation ◽  
Time Harmonic ◽  
Detailed Derivation

A new analogy between optical propagation and heat diffusion in heterogeneous anisotropic media has been proposed recently by three of the present authors. A detailed derivation of this unconventional correspondence is presented and developed. In time harmonic regime, all thermal parameters are related to optical ones in artificial metallic media, thus making possible to use numerical codes developed for optics. Then, the optical admittance formalism is extended to heat conduction in multilayered structures. The concepts of planar microcavities, diffraction gratings and planar transformation optics for heat conduction are addressed. Results and limitations of the analogy are emphasized.

QUASI‐STATIC TIME‐DOMAIN ELECTROMAGNETIC RESPONSE OF A HOMOGENEOUS CONDUCTING INFINITE CYLINDER

Geophysics ◽  
1972 ◽  
Vol 37 (1) ◽  
pp. 92-97 ◽  
Author(s):  
Saurabh K. Verma
Keyword(s):  
Time Domain ◽  
Decay Constant ◽  
Step Function ◽  
Ore Deposits ◽  
Electromagnetic Response ◽  
Infinite Cylinder ◽  
Transient Electromagnetic ◽  
Simplifying Assumptions ◽  
Time Domain Electromagnetic ◽  
Theoretical Results

Under some simplifying assumptions, the transient electromagnetic response of a homogeneous conducting infinite cylinder is derived. Two types of primary disturbances, represented by step‐function and ramp‐function pulses, are considered. Based on the theoretical results, response and decay constant curves are plotted and their utility in time‐domain electromagnetic surveys for conductive elongated ore deposits is described.

scholarly journals Effective Parameters for 1D Photonic Crystals with Isotropic and Anisotropic Magnetic Inclusions: Coherent Wave Homogenization Theory

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1475 ◽  
Author(s):  
J. Flores Méndez ◽  
A. C. Piñón Reyes ◽  
M. Moreno Moreno ◽  
A. Morales-Sánchez ◽  
Gustavo M. Minquiz ◽  
...  
Keyword(s):  
Photonic Crystals ◽  
Displacement Vector ◽  
Effective Permittivity ◽  
Homogenization Theory ◽  
Effective Parameters ◽  
Good Correspondence ◽  
Filling Fraction ◽  
Coherent Wave ◽  
Electric And Magnetic Fields ◽  
Magnetic Inclusions

A homogenization theory that can go beyond the regime of long wavelengths is proposed, namely, a theory that is still valid for vectors of waves near the edge of the first zone of Brillouin. In this paper, we consider that the displacement vector and the magnetic induction fields have averages in the volume of the cell associated with the values of the electric and magnetic fields in the edges of the cell, so they satisfy Maxwell’s equations. Applying Fourier formalism, explicit expressions were obtained for the case of a photonic crystal with arbitrary periodicity. In the case of one-dimensional (1D) photonic crystals, the expressions for the tensor of the effective bianisotropic response (effective permittivity, permeability and crossed magneto-electric tensors) are remarkably simplified. Specifically, the effective permittivity and permeability tensors are calculated for the case of 1D photonic crystals with isotropic and anisotropic magnetic inclusions. Through a numerical calculation, the dependence of these effective tensors upon the filling fraction of the magnetic inclusion is shown and analyzed. Our results show good correspondence with the approach solution of Rytov’s effective medium. The derived formulas can be very useful for the design of anisotropic systems with specific optical properties that exhibit metamaterial behavior.

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