Left-handed Material Slab Research Articles

Directional surface plasmon polaritons excited by an atom near the left-handed materials slab

Directional surface plasmon polaritons (SPP) can be realized by the spontaneous emission of an atom via a one-dimensional slab of left-handed material (LHM). By adjusting the location of the atom and the thickness of the slab, only the TE-polarized SPP modes can exist, which are distributed near the surface and propagate mainly in the surface and along the direction norm to the atomic dipole moment. Consequently, the controllable single photon with definite polarization and narrow propagation directions can be generated by means of a LHM slab with suitable parameters.

Focal Shift of Paraxial Gaussian Beams in a Left-Handed Material Slab Lens

Focal shift is inevitable in conventional lens systems due to the Fresnel number and angular aperture. In this Letter, we demonstrate that there is no focal shift when a paraxial Gaussian beam passes through a left-handed material slab lens without absorption or gain. However, the effect is exhibited in the presence of absorption or gain, and becomes larger as the absorption or gain increases. When the absorption is equal to the gain, the phenomenon of the focal shift caused by the gain is more obvious. In addition, the field distribution is not affected by the absorption or gain and always remains Gaussian both in internal and external focus planes.

Controllable optical black hole in left-handed materials

Halting and storing light by infinitely decelerating its speed, in the absence of any form of external control, is extremely di+/-cult to imagine. Here we present a theoretical prediction of a controllable optical black hole composed of a planar left-handed material slab. We reveal a criterion that the effective round-trip propagation length in one zigzag path is zero, which brings light to a complete standstill. Both theory and ab initio simulation demonstrate that this optical black hole has degrees flexible controllability for the speed of light. Surprisingly, the ab initio simulations reveal that our scheme has degrees flexible controllability for swallowing, holding, and releasing light.

Control of nonlinear self-action of high-power Gaussian beams: using a nonlinear left-handed material slab

We present the theoretical and the numerical investigations of the control effect of a left-handed material (LHM) slab with third-order nonlinearity on the nonlinear propagation and the self-focusing of high-power Gaussian beams in a conventional self-focusing Kerr medium. Analytical solutions for the beam spatial properties and the self-focusing distance are derived. It is found that, in the conventional self-focusing Kerr medium, the beam diverging and the beam converging can be enhanced and suppressed, respectively, by the nonlinear LHM slab, and both the enhancing and the suppressing can be reversed by adjusting the distance between these two media. The self-focusing is also found to be enhanced or suppressed freely, and the variation of self-focusing distance takes on an interesting waving pattern. Moreover, computer simulations demonstrate the anomalous variation of self-focusing distance with the focusing property of the incident beam.

Surface-wave mechanism of subwavelength imaging by a flat left-handed superlens

We develop a theory describing the dynamics and interaction of electromagnetic surface waves (ESWs) resonantly excited by an external source in a slab of left-handed material (LHM) with identical negative (equal to −1) values of dielectric permittivity and magnetic permeability that makes up a so-called perfect lens, or a superlens. We show that subwavelength imaging by a superlens is associated with the degeneracy of the spectrum of eigen electromagnetic surface modes at the interfaces of the metamaterial slab, whereas the dynamic response of the superlens is completely determined by the dynamics of these modes and the dispersion properties of the metamaterial. We obtain conditions that enable one to find out when a superlens produces subwavelength images of an external source. We consider the cases of a stationary and a pulse source, as well as of a source that moves with constant velocity or oscillates in space.

ABCD matrix formalism for propagation of Gaussian beam through left-handed material slab system

We apply a simple ABCD matrix formalism to investigate beam propagation in left-handed material (LHM) slab systems. Firstly, we derive the expressions for the matrix elements for a single LHM slab. Based on the ABCD matrix, we obtain the field distributions both inside and outside the LHM slab, and the conditions for focusing and phase compensation of the Gaussian beam. Secondly, the derived ABCD law is applied to analyze the propagation properties of Gaussian beams through various cascaded LHM slab systems. The corresponding focusing and phase compensation conditions of the Gaussian beam are also obtained. Our theoretic formalism may be applied as a compact and effective tool for the research of light beam propagation in complex LHM slab systems, since it avoids the complicated integral operation.

Spontaneous decay of a two-level atom near the left-handed slab

Spontaneous decay of a two-level atom near the left-handed material (LHM) slab is investigated. The contributions of the guided modes and the surface-plasmon polariton (SPP) modes supported by the LHM slab to the spontaneous decay are studied at length. We find that the atomic decay near a LHM slab is much different from that near a dielectric slab or metal slab. The first---the dielectric slab with arbitrary thickness---supports at least two guided modes (one for TE polarized and one for TM polarized), but LHM slab may support none of the guided mode for certain thickness. The second---the atom near the LHM slab---may decay through both TE- and TM-polarized SPP, but the atom near the metal slab can decay only through TM-polarized SPP. The third, when the LHM slab supports only TE-polarized SPP modes, the atom near such slab cannot couple to the SPP mode when its dipole moment is perpendicular to the interface. Even if LHM contains weak loss, above analysis is also valid, and the decay rate directly related to material's losses (defined by the decay through dissipation here) can be distinguished from the total decay rate. Most interesting, we find that the decay through SPP will be larger than the decay through dissipation when the atom is placed at an appropriate position. Our results will give constructive reference to the design and fabrication of the quantum device made of LHM.

Transmission properties of asymmetric slab waveguides with left-handed materials

A new dielectric slab waveguide with a left-handed material (LHM) cover and substrate is proposed. The dispersion relations and normalized effective thickness of the asymmetric LHM slab waveguide are investigated, in view of the normalized parameters. A number of unusual properties are found, for example, the fundamental and first-order modes do not exist and higher-order modes have double degeneracy. The propagation modes are absent at the low normalized frequency, and the cutoff frequencies of some LHM slab waveguide modes decrease with increase in the asymmetry measure. Unlike traditional slab waveguides, the V –H curves of the LHM slab waveguides are in one-to-one correspondence. Both TE and TM modes are discussed; in addition, the dispersion relations and normalized effective thicknesses of the TM modes are discussed in detail, when the difference in refractive indices of the film and the substrate is small. The results show that the region of mode coexistence taking place near the cutoff frequency becomes narrower with increase in the difference in refractive indices of the film and the substrate. The influence of this difference on the normalized effective thickness curves is different, and becomes smaller and smaller with increase in the value of the asymmetry measure, if different values of the refractive indices are employed.

Surface modes in slab waveguides with a left handed materials cover

The surface mode propagation along a dielectric slab waveguide which consists of the core and substrate of right handed materials (RHM) and the cover of left handed materials (LHM) is studied. The normalized frequency and normalized propagation constant are introduced to the left-handed material slab waveguides. The dispersion relations expressed by the normalized parameters are derived. Universal dispersion curves are obtained analytically. Based on that, the dispersion properties differ dramatically for different LHM constitutive parameters, the surface TE0 and TE1 modes are internatively obtained. It shows that two different kinds of TE modes compensate each other to form a whole mode.

Extraordinary transmission in planar waveguide loaded with anisotropic metamaterials

Ordinary planar waveguide cannot support electromagnetic (EM) wave propagating at frequency below the cut-off frequency of the waveguide, due to the evanescent wave nature of the EM wave in such waveguide. We have found by theoretical analysis that extraordinary EM wave transmission could occur for transverse-electric modes at frequency below the cut-off frequency of the hollow waveguide by inserting different kinds of anisotropic metamaterials (AMMs) in the hollow waveguide. Such transmission of EM energy has no lower cut-off frequency and is due to the conversion of the evanescent wave into propagating mode inside the AMMs, which is quite different from that in the case of waveguide loaded with an isotropic left-handed material slab. We have verified the extraordinary phenomenon by performing circuit analog of the planar waveguide loaded with different kinds of AMMs through realization with transmission line metamaterials.

左手圆环形透镜中的倏逝波

The imaging system formed by an annular left-handed material (LHM) lens as well as the evanescent waves in the lens are simulated numerically with a finite-difference time-domain (FDTD) method. For b-ag\lambda (a and b are respectively the inner and outer radii of the annular lens, and \lambda is the wavelength), when a point source is placed at an internal grid point, we demonstrate that the evanescent waves are produced around the internal interface, and cannot propagate outwards. As for b-al\lambda, the evanescent waves appear around both the internal and the external interfaces, which remarkably implies the coupling between the two interfaces. Hence it can be inferred that the evanescent waves around the external interface participating in the super-resolution imaging result from the coupling of the evanescent waves around the interface. Moreover, the partly uncomprehended properties of the evanescent waves in the LHM slab are also disclosed. It is conducive to understanding the evanescent waves in the LHMs further.

Imaging by LHM Slab Using Negative Refraction and Reflection

In this paper, we have shown a imaging system using negative refraction and reflection by Left-Handed materials (LHM) slab coated by a metal layerat one side. In this imaging system, one image is within the LHM by refraction, the other is at same side of source by reflection and refraction, which is different from the imaging only by refraction. If the LHM is slight loss and mismatch, the LHM slab can also be regarded as a perfect imaging system.

Surface modes in left-handed material slab waveguides

We present a detailed study of surface guided modes in slab waveguides with a left-handed material (LHM) core sandwiched between a right-handed cover and a right-handed substrate. Universal dispersion curves and dispersion properties are obtained analytically. It is found that the guidance properties differ remarkably for different LHM constitutive parameters. Depending on these different constitutive parameters and their relations, we consider the following three cases: (I) the absolute permeability values of both cladding layers are less than that of the core; (II) only one cladding layer has absolute permeability value less than the core; and (III) neither cladding layer has absolute permeability less than the core. The surface TE1 mode always exists in all three cases. Its dispersion curve smoothly connects with that of the oscillating TE1 mode to form a whole mode. In case I, such a whole mode exists for a very small slab thickness. In cases II and III, the whole mode behaves in the same way as other higher-order oscillating modes. The surface TE0 mode exists only in case III without cut-off and it has abnormal dispersion. A physical explanation for the propagation of guided surface modes in LHM slab waveguides is given. Both TE and TM surface guided modes are discussed.

Van der Waals interaction and spontaneous decay of an excited atom in a superlens-type geometry

Within the framework of macroscopic quantum electrodynamics, the resonant van der Waals potential experienced by an excited two-level atom near a planar magnetoelectric two-layer system consisting of a slab of left-handed material and a perfect mirror is studied. It is shown that the disregard of material absorption leads to unphysical results, with divergent values for the potential away from the surface. Under appropriate conditions, the setup is found to feature a barrier near the surface which can be employed to levitate particles or used as a trapping or cooling mechanism. Finally, the problem of spontaneous decay [K\"astel and Fleischhauer, Phys. Rev. A 68, 011804(R) (2005)] is reconsidered. Disregard of absorption is shown to drastically falsify the dependence on the atomic position of the decay rate.

A Double-Beam Radiation Leaky Wave Antenna Based on Left-Handed Material Slab with Metallic Strips Periodically Loaded

A new leaky-wave antenna structure is carefully investigated in the paper, which is based on a grounded Left-Handed material (LHM) slab periodically loaded with metal strips. A rigorous formulation similar to the spectral domain method for planar circuits is deduced to analyze the radiation characteristics of the antenna. Theoretical analysis results reveal that at specific frequency region or with proper geometrical parameters chosen, the present structure supports simultaneously two leaky modes corresponding to the forward and backward radiations. The principle of the antenna is due to the peculiar propagation properties of the unperturbed LHM grounded slab waveguide, which is totally different from the phenomenon of double or even more space harmonic mode radiations in normal periodic structures. Extensive numerical results of the leakage characteristics are given to establish useful guidelines for the design of the new type leaky wave antenna.

Generating mechanism of the energy-stream loops for the evanescent waves in a left-handed material slab

The generating mechanism of the energy-stream loops (ESLs) for the evanescent waves around the interfaces of a left-handed material (LHM) slab has been investigated with a finite-difference time-domain (FDTD) method. The simulations have shown that these ESLs originate from standing waves, attributed to the intervention of counter-propagating evanescent waves. Large numbers of ESLs can appear because of the numerous values of wave vectors k y . The larger ESLs die out more quickly than the smaller ones in time after the source is switched off, the ESLs shrink continuously with increasing delay, and the oscillated distributions of the evanescent waves between the surfaces can also be validated. It is greatly helpful for the further comprehension on energy fluxes of evanescent waves in the LHM slab.

Effects of Loss Factor on Plane Wave Propagation through a Left-Handed Material Slab

This article presents a theoretical and numerical discussion of the reflection and transmission analysis through a lossy left-handed material slab embedded between two semi-infinite dielectric media. The properties of the lossy left-handed material are given in detail and the required equations for the electromagnetic plane wave propagation are derived to solve the problem. The main important contribution of this article is the characterization of left-handed material that is different from its counterpart known in the literature. After introducing the left-handed material slab, the analytical solution is found for the powers carried by an electromagnetic wave. Then, the reflected, the transmitted, and the loss power are computed in terms of the incidence angle, the frequency, and the slab thickness in the numerical results with the emphasis on the loss factor.

Quasi-optics of the surface guided modes in a left-handed material slab waveguide

A ray model for an evanescent plane wave has been introduced to describe the property of propagation. It is found that an evanescent wave undergoes an amplitude jump during refraction and reflection on a plane interface. TE surface modes guided by a single interface and a slab waveguide containing left-handed materials are then analyzed by using a ray picture. In a slab waveguide with left-handed material cover or substrate, the odd surface mode does not exist, but there exist two even surface modes. We derive dispersion relations of TE surface guided modes according to physical principles, thus describing the surface modes purely on an intuitive and simple basis. Besides, guiding mechanics and conditions are compared between oscillating and surface guided modes.

Parametrically Shielding Electromagnetic Fields by Nonlinear Metamaterials

An analytical theory is developed for parametric interactions in metamaterial multilayer structures with simultaneous nonlinear electronic and magnetic responses and with a near-zero refractive index. We demonstrate theoretically that electromagnetic fields of certain frequencies can be parametrically shielded by a nonlinear left-handed material slab, where the permittivity and permeability are both negative. The skin depth is tunable, and even in the absence of material absorption, can be much less than the wavelength of the electromagnetic field being shielded. This exotic behavior is a consequence of the intricate nonlinear response in the left-handed materials and vanishing optical refractive index at the pump frequency.

Casimir force between left-handed-material slabs

The Casimir effect between two left-handed-material (LHM) slabs is investigated. For the LHM described by dispersive permittivity and permeability of Drude-Lorentz type, the structure of dispersion curve over negative refraction frequency band is determined by material characteristic frequencies. The bandwidth of the negative refraction characterizes the reflection property, and thus influences the Casimir effect between the slabs. Furthermore, a comparison of the Casimir forces for LHM and ordinary dielectric slabs, which have the opposite values of refractive indices at the chosen frequency, is shown. Generally, the force for LHM with sufficiently large bandwidth of negative refraction is greater than the force for ordinary dielectrics.