Non-reciprocal electromagnetic metasurface based on the nonlinearity of a liquid metamaterial.

In this Letter, we propose the design of a non-reciprocal electromagnetic metasurface, which uses a highly nonlinear liquid metamaterial as a source of non-reciprocity. We show that the proposed metasurface, whose thickness is comparable to the wavelength, can exhibit a difference between the transmission coefficients in the forward and backward directions of up to 0.95. Moreover, the particularly high nonlinearity of the liquid metamaterial enables the radiation power required to induce the nonlinear effects to be considerably reduced compared with natural materials. The feasibility of the proposed metasurface has been verified by numerical simulations.

Control of Light Transmission in a Plasmonic Liquid Metacrystal.

In this study, we experimentally demonstrated the control of light transmission through a slab of plasmonic liquid metacrystal by an external electric field. By applying the external static field, we were able to induce macroscopic anisotropy, which caused the polarization-dependent suppression of transmission at resonant frequencies. Such behavior indicates the selective plasmon excitation governed by the orientation of the meta-atoms with respect to the polarization of the electromagnetic wave. The problem of light transmission through a plasmonic liquid metacrystal was analyzed theoretically from first principles, and the obtained results were compared with the experimental data.

Spontaneous reorientations of meta-atoms and electromagnetic spatial solitons in a liquid metacrystal.

We show that transverse electromagnetic waves propagating along an external static electric field in liquid metacrystal (LMC) can provoke spontaneous rearrangement of elongated meta-atoms that changes the direction of the anisotropy axis of the LMC. This kind of instability may reorient the meta-atoms from the equilibrium state parallel to a static field to the state along a high-frequency field and back at the different threshold intensities of electromagnetic waves in such a way that bistability in the system takes place. Reorientation of meta-atoms causes a change in the effective refraction index of LMC that creates, in turn, the conditions for the formation of bright spatial solitons. Such spatial solitons are the self-consistent domains of redirected meta-atoms with trapped photons. We find that the instability thresholds as well as energy flux captured by the spatial soliton can be easily managed by variation of the static electric field applied to the LMC. We study the effects of soliton excitation and collisions via numerical simulations.

Nonlinear control of invisibility cloaking.

We introduce a new concept of the nonlinear control of invisibility cloaking. We study the scattering properties of multi-shell plasmonic nanoparticles with a nonlinear response of one of the shells, and demonstrate that the scattering cross-section of such particles can be controlled by a power of the incident electromagnetic radiation. More specifically, we can either increase or decrease the scattering cross-section by changing the intensity of the external field, as well as control the scattering efficiently and even reverse the radiation direction.

Nonlinear nanofocusing in tapered plasmonic waveguides.

We suggest using tapered waveguides for compensating losses of surface plasmon-polaritons in order to enhance nonlinear effects at the nanoscale. We study nonlinear plasmon self-focusing in tapered metal-dielectric-metal slot waveguides and demonstrate that, by an appropriate choice of the taper angle, we can effectively suppress the mode attenuation achieving stable propagation of a spatial plasmon soliton. For larger tapering angles we observe plasmon-beam nanofocusing in both spatial dimensions.

Ideal and nonideal invisibility cloaks.

We employ the analytical solutions for the spatial transformation of the electromagnetic fields to obtain and analyze explicit expressions for the structure of the electromagnetic fields in invisibility cloaks. Similar approach can be also used for analyzing beam splitters and field concentrators. We study the efficiency of nonideal electromagnetic cloaks and discuss the effect of scattering losses on the cloak invisibility.

Excitation of guided waves in layered structures with negative refraction.

We study the electromagnetic beam reflection from layered structures that include the so-called double-negative metamaterials, also called left-handed metamaterials. We predict that such structures can demonstrate a giant lateral Goos-Hänchen shift of the scattered beam accompanied by a splitting of the reflected and transmitted beams due to the resonant excitation of surface waves at the interfaces between the conventional and double-negative materials as well as due to the excitation of leaky modes in the layered structures. The beam shift can be either positive or negative, depending on the type of the guided waves excited by the incoming beam. We also perform finite-difference time-domain simulations and confirm the major effects predicted analytically.

Nonlinear transmission and spatiotemporal solitons in metamaterials with negative refraction.

We study one- and two-dimensional transmission of electromagnetic waves through a finite slab of a dielectric material with negative refraction. In the case when the dielectric slab possesses an intensitydependent nonlinear response, we observe the nonlinearity-induced wave transmission through an opaque slab accompanied by the generation of spatiotemporal solitons. We solve this problem numerically, by employing the finite-difference time-domain simulations, for the parameters of microstructured materials with the negative refractive index in the microwave region, but our results can be useful for a design of nonlinear metamaterials with the left-handed properties in other frequency range.

Defect modes and transmission properties of left-handed bandgap structures.

We analyze transmission of electromagnetic waves through a one-dimensional periodic layered structure consisting of slabs of a left-handed metamaterial and air. We derive the effective parameters of the metamaterial from a microscopic structure of wires and split-ring resonators possessing the left-handed characteristics in the microwave frequency range, and then study, by means of the transfer-matrix approach and the finite-difference time-domain numerical simulations, the transmission properties of this layered structure in a band gap associated with the zero averaged refractive index. By introducing defects, the transmission of such a structure can be made tunable, and we study the similarities and differences of the defects modes excited in two types of the band gaps.

Nonlinear surface waves in left-handed materials.

We study both linear and nonlinear surface waves localized at the interface separating a left-handed (LH) medium (i.e., a medium with both negative dielectric permittivity and negative magnetic permeability) and a conventional [or right-handed (RH)] dielectric medium. We demonstrate that the interface can support both TE- and TM-polarized surface waves-surface polaritons, and we study their properties. We describe the intensity-dependent properties of nonlinear surface waves in three different cases, i.e., when both the LH and RH media are nonlinear and when either of the media is nonlinear. In the case when both media are nonlinear, we find two types of nonlinear surface waves, one with the maximum amplitude at the interface, and the other one with two humps. In the case when one medium is nonlinear, only one type of surface wave exists, which has the maximum electric field at the interface, unlike waves in right-handed materials where the surface-wave maximum is usually shifted into a self-focusing nonlinear medium. We discuss the possibility of tuning the wave group velocity in both the linear and nonlinear cases, and show that group-velocity dispersion, which leads to pulse broadening, can be balanced by the nonlinearity of the media, so resulting in soliton propagation.

Nonlinear properties of left-handed metamaterials.

We analyze the properties of microstructured materials with negative refraction, the so-called left-handed metamaterials. We consider a two-dimensional periodic structure created by arrays of wires and split-ring resonators embedded into a nonlinear dielectric, and calculate the effective nonlinear electric permittivity and magnetic permeability. We demonstrate that the hysteresis-type dependence of the magnetic permeability on the field intensity allows changing the material properties from left- to right-handed and back. These effects can be treated as the second-order phase transitions in the transmission properties induced by the variation of an external field.