Indefinite Metamaterials Research Articles

Enhancement of lateral shift in indefinite metamaterial–insulator–metamaterial waveguides

We construct a metamaterial–insulator–metamaterial structure and study the enhancement of lateral shift or possible applications. Stationary-phase method for waveguides with indefinite metamaterial is derived and simulation results are given to discuss the properties about the proposed structure. Simulation results show that the parallel component of relative permittivity of metamaterial has much larger influence on the lateral shift than the vertical component, and the detection of lateral shift is a much more sensitive method than that of reflectivity to measure parameter changes of metamaterial.

Ultimate resolution of indefinite metamaterial flat lenses

We show that any metallo-dielectric multilayer with a hyperbolic dispersion relation can actually be characterized by a complex effective index. This refractive index, extracted from the complex Bloch band diagram, can be directly linked to the super-resolution of a flat lens made of this so- called indefinite metamaterials. This allows for a systematic optimization of the lens design, leading to structures that are outperforming state-of-art flat lenses. We show that, even when fully taking absorption into account, our design provides super-resolved images for visible light up to a distance of one wavelength from the lens edge.

Plasmonic angular momentum on metal-dielectric nano-wedges in a sectorial indefinite metamaterial

We present an analytical study in the structure-modulated plasmonic angular momentum, which is trapped in the core region of a sectorial indefinite metamaterial. This metamaterial consists of periodically arranged metal-dielectric nano-wedges along the azimuthal direction. Employing a transfer-matrix calculation and a conformal-mapping technique, our theory can deal with an arbitrary number of wedges with realistically rounded tips. We demonstrate that in the deep-subwavelength regime, strong electric fields that carry large azimuthal variations can exist only within ten-nanometer length scale around the structural center. They are naturally bounded by a characteristic radius on the order of a hundred nanometers from the center. These extreme confining properties suggest that the structure under investigation can be superior to the conventional metal-dielectric cavities in terms of nanoscale photonic manipulation.

Equivalent circuit model of radiative heat transfer

Here, we develop a theory of radiative heat transfer based on an equivalent electrical network representation for the hot material slabs in an arbitrary multilayered environment with arbitrary distribution of temperatures and electromagnetic properties among the layers. Our approach is fully equivalent to the known theories operating with the fluctuating current density, while being significantly simpler in analysis and applications. A practical example of the near-infrared heat transfer through the micron gap filled with an indefinite metamaterial is considered using the suggested method. The giant enhancement of the transferred heat compared to the case of the empty gap is shown.

Surface Tamm states in one-dimensional photonic crystals containing anisotropic indefinite metamaterials

We present a theoretical study of surface Tamm states localized at an interface that separates a semi-infinite isotropic left-handed metamaterial (LHM) and one-dimensional photonic crystal made of anisotropic indefinite metamaterial (IMM) (always-cutoff material). We discuss the dispersion properties of the Tamm states in different bandgaps and demonstrate that the cap layer, angular frequency, and arrangement of photonic crystal can provide flexible control for the dispersive properties of the Tamm states.

Influence of the orientation of optical axis on the transmission properties of one-dimensional photonic crystals containing uniaxial indefinite metamaterial

The transmission properties of a one-dimensional photonic crystal containing uniaxial indefinite metamaterial are investigated using the transfer matrix method. It is shown that the photonic bandgaps of the structure strongly depend on the orientation of the optical axis of the indefinite metamaterial. The results show that it is possible to obtain the Brewster condition for both TE and TM polarizations. This condition noticeably affects the profiles of the electromagnetic field inside the one-dimensional periodic structure.

Gouy phase of optical beams in anisotropic indefinite metamaterials

The Gouy phase shift of optical beams in anisotropic indefinite metamaterials displays extraordinary characteristics because of the presence of anisotropic magnetic and electric responses. We propose a simple interpretation of these characteristics from the unusual dispersion relation of the optical waves in the metamaterials, which influences the expectation value of the axial propagation constant of the focused beam.

Nanoscale metamaterial optical waveguides with ultrahigh refractive indices

We propose deep-subwavelength optical waveguides based on metal-dielectric multilayer indefinite metamaterials with ultrahigh effective refractive indices. Waveguide modes with different mode orders are systematically analyzed with numerical simulations based on both metal-dielectric multilayer structures and the effective medium approach. The dependences of waveguide mode indices, propagation lengths and mode areas on different mode orders, free space wavelengths and sizes of waveguide cross sections are studied. Furthermore, waveguide modes are also illustrated with iso-frequency contours in the wave vector space in order to investigate the mechanism of waveguide mode cutoff for high order modes. The deep-subwavelength optical waveguide with a size smaller than {\lambda}0/50 and a mode area in the order of 10-4 {\lambda}02 is realized, and an ultrahigh effective refractive index up to 62.0 is achieved at the telecommunication wavelength. This new type of metamaterial optical waveguide opens up opportunities for various applications in enhanced light-matter interactions.

Design, fabrication and characterization of indefinite metamaterials of nanowires

Indefinite optical properties, which are typically characterized by hyperbolic dispersion relations, have not been observed in naturally occurring materials, but can be realized through a metamaterial approach. We present here the design, fabrication and characterization of nanowire metamaterials with indefinite permittivity, in which all-angle negative refraction of light is observed. The bottom-up fabrication technique, which applies electrochemical plating of nanowires in porous alumina template, is developed and demonstrated in achieving uniform hyperbolic optical properties at a large scale. We developed techniques to improve the uniformity and to reduce the defect density in the sample. The non-magnetic design and the off-resonance operation of the nanowire metamaterials significantly reduce the energy loss of electromagnetic waves and make the broad-band negative refraction of light possible.

Super Talbot effect in indefinite metamaterial

The Talbot effect (or the self-imaging effect) can be observed for a periodic object with a pitch larger than the diffraction limit of an imaging system, where the paraxial approximation is applied. In this paper, we show that the super Talbot effect can be achieved in an indefinite metamaterial even when the period is much smaller than the diffraction limit in both two-dimensional and three-dimensional numerical simulations, where the paraxial approximation is not applied. This is attributed to the evanescent waves, which carry the information about subwavelength features of the object, can be converted into propagating waves and then conveyed to far field by the metamaterial, where the permittivity in the propagation direction is negative while the transverse ones are positive. The indefinite metamaterial can be approximated by a system of thin, alternating multilayer metal and insulator (MMI) stack. As long as the loss of the metamaterial is small enough, deep subwavelength image size can be obtained in the super Talbot effect.

Subwavelength Plasmon Microcavity Based on the Indefinite Metamaterial Waveguide

The resonance properties of surface plasmon in the IMM/dielectric/IMM waveguide are theoretically studied by using finite-difference time-domain technique, where the claddings are indefinite metamaterials (IMMs). From the dispersion relation, it is found that the IMM/dielectric/IMM waveguide supports TE polarized surface plasmon if IMM is always-cutoff with negative permeability. For an IMM/dielectric/IMM waveguide with a finite length, a subwavelength plasmon microcavity can be formed by Fabry-Perot resonance. At the resonant frequency, the magnetic field is maximized at the dielectric core entrance and exit, the electromagnetic energy is strongly concentrated around the dielectric core. When an artificial magnetic resonator is put at the core entrance and the resonance frequency is tuned to the plasmon microcavity mode, Rabi splitting can appear because of the strong coupling between this resonator and the cavity mode.

Transformation of nonlinear behaviors: From bright- to dark-gap soliton in a one-dimensional photonic crystal containing a nonlinear indefinite metamaterial defect

Nonlinear propagation characteristics are investigated theoretically in a one-dimensional photonic band-gap structure doped with a nonlinear indefinite metamaterial defect for five distinct frequency intervals. It is found from the electric field distribution that there exists the bright gap solitonlike when the nonlinear indefinite metamaterial defect is a cut-off medium, while the dark gap solitonlike can appear in the nonlinear never cut-off defect layer. It is also found that there exists corresponding bistable lateral shift the properties of which are strongly dependent on the permittivity and permeability of nonlinear indefinite metamaterials. Moreover, in contrast to the switch-down threshold value, the switch-up threshold value is more sensitive to the incident frequency.

Transmission properties of Fibonacci quasi-periodic one-dimensional photonic crystals containing indefinite metamaterials

The transmission properties of Fibonacci quasi-periodic one-dimensional photonic crystals (1DPCs) containing indefinite metamaterials are theoretically studied. It is found that 1DPCs can possess an omnidirectional zero average index (zero- n̅) gap which exists in all Fibonacci sequences. In contrast to Bragg gaps, such zero- n̅ gap is less sensitive to the incidence angle, the scale length and the polarizations of electromagnetic waves. When an impurity is introduced, a defect mode appears inside the zero- n̅ gap with a very weak dependence on the incidence angle and scaling.

Metric Signature Transitions in Optical Metamaterials

We demonstrate that the extraordinary waves in indefinite metamaterials experience an (--++) effective metric signature. During a metric signature change transition in such a metamaterial, a Minkowski space-time is created together with a large number of particles populating the space-time. Such metamaterial models provide a tabletop realization of metric signature change events suggested to occur in Bose-Einstein condensates and quantum gravity theories.

Low loss negative refraction metamaterial using a close arrangement of split-ring resonator arrays

In this work, we realize a low loss negative refraction using indefinite metamaterial of a close arrangement of split-ring resonator (SRR) arrays. A beam shift experiment has been performed to verify the negative refraction and demonstrate the low loss property. The enhanced magnetic resonance between two neighbouring SRRs broadens the resonance range and produces a frequency range with low loss. Transmission properties of the metamaterial are also analysed to characterize the negative refraction around the resonance frequency in detail.

Opposite Goos—Hänchen Displacements for TE- and TM-Polarized Beams Transmitting through a Slab of Indefinite Metamaterial

The Goos–Hänchen displacement of a light beam transmitting through an indefinite metamaterial slab is studied. The results indicate that the displacement would be negative or positive for different parameters, and the necessary conditions for negative or positive displacements are summarized. Due to the special anisotropic properties, the directions of displacements for different polarization beams are opposite by proper design. In addition, the simultaneously enhanced positive and negative displacements will appear at different resonant angles under consideration of the active slab. These phenomena could have convenient applications in optical devices.

Modulation of bistable lateral shifts in a one-dimensional nonlinear photonic crystal consisting of indefinite metamaterials

Nonlinear propagation characteristics are investigated theoretically in a one-dimensional photonic band-gap structure containing indefinite metamaterials. It is found that optical bistability can be achieved at very low threshold values of normalized input intensity in this composite structure when the indefinite metamaterial is a cut-off, anticut-off, and never cut-off medium. It is also found that there exists corresponding bistable lateral shift which is strongly dependent on the parameters of indefinite metamaterials.

Unusual photon tunneling in the frustrated total internal reflection structure includingindefinite metamaterials

The transmittance and the behavior of an evanescent field in the frustrated total internalreflection structure composed of isotropic media and anisotropic indefinite metamaterial areobtained by the transfer matrix formulation. The evanescent waves can evolve into differentforms associated with the different dispersion relations of the indefinite metamaterial. Incutoff and anti-cutoff media, the evanescent waves are amplified and even total photontunneling is obtained under some conditions. Then the evanescent wave can be transformedinto a propagation wave and highly efficient tunneling is also achieved in a always-cutoffmedium.

Partial focusing by indefinite complementary metamaterials

We have experimentally realized a two-dimensional partial focusing within a planar waveguide using complementary indefinite metamaterials. When the electric fields emitted from the dipole are TE polarized, the focusing condition requires negative magnetic response in the propagation direction of the waveguide, which can be achieved by the complementary electric resonator (CELC) structures. We have carefully designed the experimental configurations and the dimensions for the CELC structures. The experimental result is consistent with the theoretical prediction, which validates the partial focusing phenomenon.

Properties of omnidirectional gap and defect mode of one-dimensional photonic crystal containing indefinite metamaterials with a hyperbolic dispersion

The structure of one-dimensional photonic crystal (1DPC) containing indefinite metamaterials with a hyperbolic dispersion relation is proposed to realize the omnidirectional gap for the design of omnidirectional reflectors and filters. It is demonstrated that this 1DPC can result in a similar zero average index (zero-n¯) gap usually appearing in the 1DPC containing isotropic left-handed materials. The properties of zero-n¯ gap and defect modes of this photonic crystal are studied in detail. The edge of this zero-n¯ gap is insensitive to incident angle and polarization of light in contrast to the Bragg gap. When a defect layer is introduced into the 1DPC, a defect mode appears inside the omnidirectional gap. The spectral position of defect mode is found to be weakly dependent on the incident angle of light and nearly invariant to the scale length of photonic crystal.