Ilya V. Shadrivov

Wide-band negative permeability of nonlinear metamaterials

We propose a novel way to achieve an exceptionally wide frequency range where metamaterial possesses negative effective permeability. This can be achieved by employing a nonlinear response of metamaterials. We demonstrate that, with an appropriate design, a frequency band exceeding 100% is available for a range of signal amplitudes. Our proposal provides a significant improvement over the linear approach, opening a road towards broadband negative refraction and its applications.

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.

Guided modes in negative refractive index waveguides

We reveal that guided waves in negative-refraction-index (left-handed) waveguides possess a number of peculiar properties such as the absence of the fundamental modes, mode double degeneracy, and sign-varying energy flux. We predict the existence of novel types of guided waves with a dipole-vortex structure of the Pointing vector.

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.

Tunable split-ring resonators for nonlinear negative-index metamaterials

We study experimentally the dynamic tunability and self-induced nonlinearity of split-ring resonators incorporating variable capacitance diodes. We demonstrate that the eigenfrequencies of the resonators can be tuned over a wide frequency range, and significantly, we show that the self-induced nonlinear effects observed in the varactor-loaded split-ring resonator structures can appear at relatively low power levels.

Giant Goos-Hänchen effect at the reflection from left-handed metamaterials

We study the beam reflection from a layered structure with a left-handed metamaterial. We predict a giant lateral (Goos-Hanchen) shift and splitting of the beam due to the resonant excitation of surface polaritons with a vortexlike energy flow between the right- and left-handed materials.

Hyperbolic metamaterials based on multilayer graphene structures

We suggest a new class of hyperbolic metamaterials for THz frequencies based on multilayer graphene structures. We calculate the dielectric permittivity tensor of the effective nonlocal medium with a periodic stack of graphene layers and demonstrate that tuning from elliptic to hyperbolic dispersion can be achieved with an external gate voltage. We reveal that such graphene structures can demonstrate a giant Purcell effect that can be used for boosting the THz emission in semiconductor devices. Tunability of these structures can be enhanced further with an external magnetic field which leads to the unconventional hybridization of the TE and TM polarized waves.

Structural tunability in metamaterials

We propose an efficient approach for tuning the transmission characteristics of metamaterials through a continuous adjustment of the lattice structure and confirm it experimentally in the microwave range. The concept is rather general and applicable to various metamaterials as long as the effective medium description is valid. The demonstrated continuous tuning of a metamaterial response is highly desirable for a number of emerging applications of metamaterials, including sensors, filters, and switches, realizable in a wide frequency range.

Magnetoelastic nonlinear metamaterials

We propose and demonstrate experimentally a novel type of nonlinearity in metamaterials, which is induced by mechanical deformation of the structure. The nonlinearity arises from the introduction of an extra degree of freedom in the metamaterial, which allows for elastic displacement of the strongly interacting structural elements (see Fig. 1a). This type of nonlinearity relies on the counterplay between the electromagnetic attraction and the elastic repulsion, and the induced deformation alters the electromagnetic response of the entire structure, leading to the novel nonlinear response of the metamaterial.

Tunable transmission and harmonic generation in nonlinear metamaterials

We study the properties of a tunable nonlinear metamaterial operating at microwave frequencies. We fabricate the nonlinear metamaterial composed of double split-ring resonators and wires where a varactor diode is introduced into each resonator so that the magnetic resonance can be tuned dynamically by varying the input power. We show that at higher powers the transmission of the metamaterial becomes power dependent, and we demonstrate experimentally power-dependent transmission properties and selective generation of higher harmonics.