Left-handed Materials Research Articles

Optical Solitons with Beta and M-Truncated Derivatives in Nonlinear Negative-Index Materials with Bohm Potential.

In this article, we explore solitary wave structures in nonlinear negative-index materials with beta and M-truncated fractional derivatives with the existence of a Bohm potential. The consideration of Bohm potential produced quantum phase behavior in electromagnetic waves. The applied technique is the New extended algebraic method. By use of this approach, acquired solutions convey various types of new families containing dark, dark-singular, dark-bright, and singular solutions of Type 1 and 2. Moreover, the constraint conditions for the presence of the obtained solutions are a side-effect of this technique. Finally, graphical structures are depicted.

Cancer cell detector based on a slab waveguide of anisotropic, lossy, and dispersive left-handed material

Cancer is a disease that takes place when human cells grow uncontrollably. When detected and cured early, it can be non-life-threatening. It becomes life-threatening in case of late discovery where it affects the ability of an organ to function. In this work, a symmetric slab waveguide sensor is analyzed for the detection of cancer cells. The covering layers are assumed anisotropic lossy dispersive left-handed materials. Different from other sensors in which the analyte is located in the cladding region where the evanescent field exists, the cancerous cell is placed in the guiding film region that supports the oscillating field. Hence, the proposed sensor avoids the acute weakness of conventional optical waveguide sensors. Due to the high localization of the electromagnetic wave in the analyte region, the proposed sensor shows unusual sensitivity enhancement. The results revealed that the sensitivities obtained are 110%, 325%, and 450% for the first, second, and third modes, respectively. The enhancement of the sensitivity of the third mode relative to the conventional waveguide sensors is nearly a factor of 18.

Chirped periodic and solitary waves in nonlinear negative index materials

Propagation of ultrashort pulses at least a few tens of optical cycles in duration through a negative index material is investigated theoretically based on the generalized nonlinear Schrödinger equation with pseudo-quintic nonlinearity and self-steepening effect. Novel periodic waves of different forms are shown to exist in the system in the presence of higher-order effects. It is found that such periodic structures exhibit an interesting chirping property which depends on the light field intensity. The nonlinearity in pulse chirp is found to be caused by the presence of self-steepening effect in the negative index medium. The solutions also comprise dark, bright, and kink solitary waves. Stability of the solitary wave solutions are proved analytically using the theory of nonlinear dispersive waves. The stability of the solutions is numerically studied under finite initial perturbations.

Modulation instability in one-dimensional bi-periodic optical lattice made of negative index metamaterials waveguide arrays

In this paper, the dispersion relation and modulation instability (MI) have been studied in one-dimensional bi-periodic optical lattice of negative index metamaterials waveguide arrays. It is found that the plateaus will be appeared on the dispersion curve when the coupling coefficient is around 0.25. The plateau will become wider with the increase of the nonlinear and longitudinal modulation depth. The phase shift has little effect on MI the gain spectrum when the values of coupling coefficient, nonlinear coefficient and longitudinal modulation depth coefficient are in the range that is conducive to the generation of plateaus. However, if the values of these coefficients are in the range that is not conducive to the generation of plateaus, the effect of phase shift on the MI gain spectrum will become significant. In addition, it is found that the inverse periodic modulation between waveguides causes the light intensity to change periodically during transmission.

Negative Index Metamaterial Lens for Subwavelength Microwave Detection

Metamaterials are engineered periodic structures designed to have unique properties not encountered in naturally occurring materials. One such unusual property of metamaterials is the ability to exhibit negative refractive index over a prescribed range of frequencies. A lens made of negative refractive index metamaterials can achieve resolution beyond the diffraction limit. This paper presents the design of a metamaterial lens and its use in far-field microwave imaging for subwavelength defect detection in nondestructive evaluation (NDE). Theoretical formulation and numerical studies of the metamaterial lens design are presented followed by experimental demonstration and characterization of metamaterial behavior. Finally, a microwave homodyne receiver-based system is used in conjunction with the metamaterial lens to develop a far-field microwave NDE sensor system. A subwavelength focal spot of size 0.82λ was obtained. The system is shown to be sensitive to a defect of size 0.17λ × 0.06λ in a Teflon sample. Consecutive positions of the defect with a separation of 0.23λ was resolvable using the proposed system.

Invisible Gateway by Superscattering Effect of Metamaterials

Illusion devices, such as superscatterer and invisible gateway, have been theoretically studied under the theory of transformation optics and folded geometry transformations. The realization of these devices needs building blocks of metamaterials with negative permittivities and permeabilities. However, superscattering effects, such as stopping wave propagation in an air channel, have not been verified from illusion devices physically because of the challenge of metamaterial design, fabrication, and material loss. In this Letter, we implement a big metamaterial superscatterer, and experimentally demonstrate its superscattering effect at microwave frequencies by field-mapping technology. We confirm that superscattering is originated from the excitation of surface plasmons. Integrated with superscatterer, we experimentally display that an invisible gateway could stop electromagnetic waves in an air channel with a width much larger than the cutoff width of the corresponding rectangular waveguide. Our results provide a first direct observation of superscattering effect of double negative metamaterials and invisible gateway for electromagnetic waves. It builds up an ideal platform for future designs of other illusion devices.

Active control of the hybridization effect of near-field coupled resonators in metamaterial for a tunable negative refractive index at terahertz frequencies

To achieve broadband negative refraction, which is useful for many practical applications, recent studies have shown that the use of hybridization is one of the most effective methods. Nevertheless, reported studies often propose changing structural parameters rather than external factors. In this article, a method to control actively the bandwidth of negative refractive index (NRI) metamaterials based on second-order hybridization operating in the terahertz regime is proposed numerically by use of a simple disk-grid dimer. By use of the semiconductor InSb as the metallic component, the conductivity is tunable according to temperature, which changes the separation of magnetic resonant frequencies in second-order hybridization scheme and the plasma frequency of metamaterial. Consequently, the fractional bandwidth of the double-NRI region is extended. The mechanism of the phenomenon is explained clearly by both calculations and simulation. Finally, the fractional bandwidth of the NRI region was optimized by variation of the dielectric thickness of the disk-grid monomer and the thickness of the interlayer between the two monomers. The optimal fractional bandwidth is 10.4%, with a high transmitted power of 94% and a high figure of merit of 52.9 at 1.68 THz. Our results pave the way for the implementation of diverse semiconductors in tunable broadband NRI metamaterials at terahertz frequencies.

CPW fed metamaterial loaded dual‐band roof‐top antenna for vehicular communications

A dual-band monopole antenna exploiting the use of a novel double-negative metamaterial is discussed in this article for use in vehicular communications. The proposed unit cell consists of an H-cell resonator sandwiched between two inverted “E” shaped resonator connected to a “T” stub. The proposed unit cell exhibits double negative property from 3.4 to 5 GHz. The dual-band property is achieved by loading the monopole with the proposed metamaterial. The loaded monopole antenna offers dual-band property with resonance at 2.4 and 3.8 GHz making the antenna suitable for terrestrial communications in automobiles. Along with dual-band property, the proposed antenna also offers miniaturization through frequency reduction. The prototype antenna is fabricated and the simulation results are validated using experimental measurements. The proposed antenna offers 6% and 9.15% measured impedance bandwidth with voltage standing wave ratio less than 2 and realized antenna gain greater than 3.2 dBi. Furthermore, the impact of the vehicle's body on the antenna performance is simulated and the results are presented.

Theoretical circuit modeling of tetra bands DNG metamaterial by transmission line theory with very small frequency

Theoretical circuit modeling of tetra bands DNG metamaterial by transmission line theory with very small frequency

Chiral interaction of an atom in a sandwiched waveguide.

The chiral interaction between light and matter is mainly caused by the spin-momentum locking and makes the chiral quantum optics enter a vigorous development stage. Here, we explore the condition of the perfect chiral interaction between an atom possessing circular dipole and the surface plasmon polariton (SPP) mode. The realization of the perfect chiral interaction must satisfy the following two conditions at the same time. First, the SPP mode should possess the transverse circular polarization; and second, the atom decays mainly into the SPP mode, while the decay through other channel can be ignored. In this paper, we adopt a simple but effective structure to satisfy both of requirements, which is the sandwiched waveguide made of metal. We found that the transverse circular polarization of SPP mode might be achieved within the structure possessing multiple interfaces instead of the interface separating two semi-infinite materials. In our model, the decay rate into SPP mode overwhelms that through traveling wave, which provides higher quantum efficiency. What's more, we found that only the symmetric TM-polarized SPP mode might get the transverse circular polarization. For the sandwiched structure containing metal, the existence of two SPP modes weakens the overall chiral interaction. However, the structure containing left-handed materials (LHMs), which can only support one symmetric TM-polarized SPP mode, can get the nearly perfect chiral interaction. We measure the chiral interaction through the decay rate, radiation field distribution and the unidirectional rate through the energy flux. Our work provides a reference for exploring the perfect chiral interaction in more complex structures and has potential and wide applicability to other optical processes.

Metallic ferromagnetic selenospinel composites of CuCr2Se4–CdCr2Se4 with double negative electromagnetic parameters

Random metamaterial with negative electric permittivity (ε < 0) and negative magnetic permeability (μ < 0) is a group of attractive alternatives to ordered double negative metamaterials (DNMs) with periodic unit cells; however, the preparation of random DNMs with a relatively convenient preparation process and their electromagnetic property adjustment are of challenge. Here, we report the preparation of metallic ferromagnetic selenospinel composites, xCdCr2Se4·(1−x)CuCr2Se4, from metallic powders by using a simple solid-state reaction process, and double negative ε and μ have been observed in the frequency range of 120–650 MHz for 0.2CdCr2Se4·0.8CuCr2Se4 and 73–520 MHz for 0.4CdCr2Se4·0.6CuCr2Se4. The negative ε is owing to the plasmonic state of delocalized carriers in the metallic ferromagnetic CuCr2Se4, which can be described with the Drude model. The suppression of the magnetic resonance induced by the eddy current has been alleviated by the proper addition of the paramagnetic semiconductor CdCr2Se4. A theoretical model deduced from Maxwell's equation has been constructed based on the skin effect to elucidate the magnetic resonance-dependent negative permeability. Our work introduces the metallic ferromagnetic chalcospinels into the field of random DNMs and sheds light on the theoretical understanding and tuning mechanism on the double negative properties.

Reduced linear viscoelastic isotropic Cosserat medium with rotational viscosity: an acoustic metamaterial

In this paper we investigate the influence of rotational viscosity on the plane shear-rotational wave propagation in the linear isotropic reduced Cosserat medium. In such a continuum body points possess independent rotational and translational degrees of freedom, but the material does not resist to the gradient of microrotation. Stress tensor is asymmetric, but the couple stress is zero. For the elastic reduced Cosserat medium a band gap is present, where no running waves exist, and the logarithmic decrement is infinitely large. It was shown before that introducing viscoelasticity we may qualitatively change the dispersion behaviour. This work investigates the case of rotational viscosity, related to the difference between micro- and macrorotation. We show that in this case running decaying waves appear in the band gap domain, and their logarithmic decrement becomes finite. The dispersion relation for the real part of the wave number has a decreasing part. This means that the group velocity of these waves is opposed to their phase velocity, the behaviour characterizing double negative acoustic metamaterials.

Synthesis and characterization of Mg\u2013Zn ferrite based flexible microwave composites and its application as SNG metamaterial

In this article, we propose SNG (single negative) metamaterial fabricated on Mg–Zn ferrite-based flexible microwave composites. Firstly, the flexible composites are synthesized by the sol-gel method having four different molecular compositions of MgxZn(1−x)Fe2O4, which are denoted as Mg20, Mg40, Mg60, and Mg80. The structural, morphological, and microwave properties of the synthesized flexible composites are analyzed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and conventional dielectric assessment kit (DAK) to justify their possible application as dielectric substrate at microwave frequency regime. Thus the average grain size is found from 20 to 24 nm, and the dielectric constants are 6.01, 5.10, 4.19, and 3.28, as well as loss tangents, are 0.002, 0.004, 0.006, and 0.008 for the prepared Mg–Zn ferrites, i.e., Mg20, Mg40, Mg60, and Mg80 respectively. Besides, the prepared low-cost Mg–Zn ferrite composites exhibit high flexibility and lightweight, which makes them a potential candidate as a metamaterial substrate. Furthermore, a single negative (SNG) metamaterial unit cell is fabricated on the prepared, flexible microwave composites, and their essential electromagnetic behaviors are observed. Very good effective medium ratios (EMR) vales are obtained from 14.65 to 18.47, which ensure the compactness of the fabricated prototypes with a physical dimension of 8 × 6.5 mm2. Also, the proposed materials have shown better performances comparing with conventional FR4 and RO4533 materials, and they have covered S-, C-, X-, Ku-, and K-band of microwave frequency region. Thus, the prepared, flexible SNG metamaterials on MgxZn(1−x)Fe2O4 composites are suitable for microwave and flexible technologies.

Saturable higher nonlinearity effects on the modulational instabilities in three-core triangular configuration couplers

This paper demonstrates the possibility to observe the modulational instability (MI) regions due to modified nonlinear saturability over and above other high-order nonlinearities for the triangular configuration of a three-core oppositely directed coupler. In this configuration, two channels are positive-refractive-index material, and one is a negative-index material. The governing equations are the modified coupled nonlinear Schrödinger equations, to which we add the higher-order nonlinearity terms and coupling terms. This equation is further modified with the saturable nonlinearity term. In the presence of several nonlinearities, we derive the dispersion relation for the optical coupler under consideration. We use a linear stability analysis to study the modulation stability characteristic gain in both the normal and anomalous group-velocity dispersion regimes. We have widely varied the parameter range of the physical system parameters to accommodate different possibilities. In the normal region, the saturable nonlinearity aids in increasing the bandwidth of the MI region, while in the anomalous regime, the bandwidth reduces. In the normal dispersion case, the simultaneous presence of all nonlinearities in the optical coupler does not provide a suitable scope for pulse propagation. On the other hand, in the anomalous regime, these nonlinearities favor for pulse propagation.

Parameter modulation of periodic waves and solitons in metamaterials with higher-order dispersive and nonlinear effects

A generalized nonlinear Schrodinger equation with higher-order dispersive and nonlinear effects is presented to govern the pulse propagation in negative index materials. Via the mapping method, Jacobian elliptic function solutions and their corresponding soliton solutions are found. Parameter modulation of higher-order dispersive effect and nonlinearities for periodic waves and solitons is studied. With the addition of the third dispersion parameter, or the quintic nonlinear parameter, the change of real and imaginary parts of periodic waves and solitons is same; namely, their amplitudes increase, and yet their widths decrease. Moreover, phase transitions of solutions with parameter modulation are found.

“Quad-band flexible magnesium zinc ferrite (MgZnFe2O4)-based double negative metamaterial for microwave applications”

This article presents vertically coupled, rectangular complementary split-ring resonator-shaped quad-band double-negative (DNG) metamaterial unit cells, that is, having both negative permittivity and permeability, which redirect negative refractive and also are not found in nature. The metamaterial is fabricated on magnesium zinc ferrite-based flexible microwave substrates, and the flexible substrates are chosen with two different concentrations of magnesium (Mg) denoted by Mg30 and Mg50 for 30% and 50% of Mg, which possess dielectric constants of 4.32 and 3.15 and loss tangents of 0.003 and 0.005, respectively. The proposed metamaterials are demonstrated by utilizing the CST microwave simulator, and their effective parameters are extracted according to the Nicolson-Ross-Wire method. With Mg30, the prepared, flexible metamaterial shows measured resonances at 3.70 GHz, 7 GHz, 8.60 GHz, and 9.78 GHz, whereas with Mg50 it shows the measured resonances at 4.10 GHz, 7.70 GHz, 9.33 GHz, and 10.62 GHz. Very good effective medium ratios (EMR) along with DNG properties are obtained, namely 6.5 and 5.85 for Mg30 and Mg50, respectively, with a physical dimension of 12.5 × 9.5 mm2 for both of the unit cells. Also, the electric field, magnetic field, and surface current distribution at different resonances and the polarization insensitivity at different polarization angles were observed. Thus, the designed new flexible substrate microwave materials based on DNG metamaterials are potential candidates for S-, C- and X-band applications, as well as for flexible microwave technologies.

Mathematical modeling of antireflection coating based on double negative index materials

New artificial Negative index materials (NIMs) or metamaterials have rapidly attracted researchers and industry due to their unusual properties. Applications of various NIMs have been found to be used in manufacturing and design some nano devices such as optical sensors and solar cells. The concept of solar cells depends on the maximizing the light transmission and minimizing the reflection. We propose solar cell structure model based on NIMs to enhance the light efficiency in solar cells. The proposed structure consists of four layers including two NIMs layers called Double NIMs. The simulation of the proposed model has been done utilizing the Transfer Matrix Method (TMM). High transmission and low reflection have been obtained. Solar cells based on double NIMs show promising future and could successfully be used to design highly efficient solar cells.

Tunable surface waves supported by graphene-covered left-handed material structures

The active tuning of surface waves supported by left-handed materials (LHMs) is a major challenge for their practical applications and usability, and graphene has been proposed as an agent for the active tuning of surface waves. In this study, tunable surface waves supported by graphene-layered LHM structures are investigated theoretically. The analytical and numerical results are computed for transverse electric (TE) and transverse magnetic (TM)-polarized surface waves. According to the spectral range, two configurations of LHMs (i.e., gigahertz (GHz)-LHM and terahertz (THz)-LHM) are discussed. The physical modeling of graphene is done using the conductivity model based on random phase approximation-based Kubo formalism. The split ring resonator (SRR) model and Kramers–Kronig relations-based causality principle are used for the physical realization of LHMs. To simulate the graphene-layered LHM interface, impedance boundary conditions (IBCs) are applied. Numerical results are computed for dispersion curves, effective wave numbers, and field profiles of surface waves supported by graphene-covered GHz-LHM and THz-LHM. The influence of graphene parameters on the resonance frequency, dispersion curves, and confinement characteristics of surface waves is analyzed for both configurations of LHMs. It is concluded that the graphene-covered GHz-LHM structure supports the tunable surface waves as surface plasmon polaritons (SPPs) support TM-polarized waves. However, with the TE-polarized surface wave, the structure supports the surface polaritons, which do not depend upon the graphene parameters. For the case of the graphene-covered THz-LHM structure, it is concluded that the structure supports the plasmon modes for both polarized waves and the resonance frequency ranges from THz to infrared (IR). The confinement of the TE-polarized surface waves on the graphene layer can be enhanced up to fourfold as compared to the suspended monolayer graphene by using a THz-LHM substrate. Further, the numerical results are found to be consistent with the literature under special conditions. The proposed graphene-layered LHM structure may have potential uses in the active tuning of surface waves, near-field communication and imaging devices, surface waveguide design, and LHM-based metasurfaces.

Propagation dynamics of vortex electromagnetic waves in dispersive left-handed materials

The interactions between electromagnetic (EM) waves and Metamaterials have always been considered as research focus of electronic information science and technology. In this work, we focus on the dynamical properties of EM waves with vortex structure propagating in left-handed materials (LHMs) exhibiting dispersive characteristics. The analytical expressions for the electric and magnetic field components of vortex EM waves without the limitation of the paraxial condition are derived using the spectral domain method. A canonical approach is utilized to explore the dynamical properties, including the energy, momentum, spin and orbital angular momentum, of vortex EM waves in dispersive LHMs. Numerical results show that the orientation of transverse energy flow in the LHM is reversed compared to that in the free space. The waves with higher angular frequency are beneficial to improve the dynamical characteristics. Furthermore, the topological charge and polarization state have a significant effect on the dynamical quantities. This study is expected to provide useful insights into the interactions of vortex EM waves with metamaterials, and their further applications.

Design and Fabrication of Negative-Refractive-Index Metamaterial Unit Cells for Near-Megahertz Enhanced Acoustic Transmission in Biomedical Ultrasound Applications

Acoustic metamaterials with negative index of refraction offer great potential for improving resolution and signal transmission in biomedical ultrasound. Their potential has remained unrealized, however, for the lack of a fabrication technology that can create metamaterials compatible with biomedical imaging and operating at frequencies near 1 MHz. The authors report the simulation, fabrication, and characterization of integrated Helmholtz and membrane resonators with characteristic lengths less than 1 mm, produced by silicon-based clean-room microfabrication. Their work finally realizes a negative-index acoustic metamaterial that can be applied in ultrasound imaging and therapeutics.