Self-oscillations in nonlinear torsional metamaterials

We study the nonlinear dynamics of torsional meta-molecules - sub-wavelength resonators with strong coupling between electromagnetic excitation and rotational deformation - and show that such structures may undergo self-oscillations. We develop a semi-analytical model to evaluate the electromagnetic-elastic coupling in such structures. By analysing the local stability of the system, we reveal two different mechanisms leading to self-oscillations. Contrary to many previously studied optomechanical systems, self-oscillations of torsional meta-molecules can be extremely robust against mechanical damping. Due to the chiral nature of the structure, a consequence of self-oscillations in this system is dynamic nonlinear optical activity, which can be actively controlled by a range of parameters such as the field strength and polarization of the incident wave. © IOP Publishing and Deutsche Physikalische Gesellschaft

Nonlinear response via intrinsic rotation in metamaterials

We propose and experimentally verify a way to achieve strong nonlinear coupling between the electromagnetic and elastic properties in metamaterials. This coupling is provided through a novel degree of freedom in metamaterial design: the internal rotation within structural elements. Our meta-atoms have high sensitivity to electromagnetic wave power, and the elastic and electromagnetic properties can be independently designed to optimize the response. We demonstrate a rich range of nonlinear phenomena including self-tuning and bistability, and provide a comprehensive experimental demonstration of the predicted effects. © 2013 American Physical Society

Suppression of Anderson localization in disordered metamaterials

We study wave propagation in mixed, 1D disordered stacks of alternating right- and left-handed layers and reveal that the introduction of metamaterials substantially suppresses Anderson localization. At long wavelengths, the localization length in mixed stacks is orders of magnitude larger than for normal structures, proportional to the sixth power of the wavelength, in contrast to the usual quadratic wavelength dependence of normal systems. Suppression of localization is also exemplified in long-wavelength resonances which largely disappear when left-handed materials are introduced. © 2007 The American Physical Society

Strongly anisotropic media: the THz perspectives of left-handed materials

We demonstrate that non-magnetic ($\mu \equiv 1$) left-handed materials can be effectively used for waveguide imaging systems. We also propose a specific THz realization of the non-magnetic left-handed material based on homogeneous, naturally-occurring media

Nonlinear Localization in Metamaterials

Metamaterials, i.e., artificially structured ("synthetic") media comprising weakly coupled discrete elements, exhibit extraordinary properties and they hold a great promise for novel applications including super-resolution imaging, cloaking, hyperlensing, and optical transformation. Nonlinearity adds a new degree of freedom for metamaterial design that allows for tuneability and multistability, properties that may offer altogether new functionalities and electromagnetic characteristics. The combination of discreteness and nonlinearity may lead to intrinsic localization of the type of discrete breather in metallic, SQUID-based, and ${\cal PT}-$symmetric metamaterials. We review recent results demonstrating the generic appearance of breather excitations in these systems resulting from power-balance between intrinsic losses and input power, either by proper initialization or by purely dynamical procedures. Breather properties peculiar to each particular system are identified and discussed. Recent progress in the fabrication of low-loss, active and superconducting metamaterials, makes the experimental observation of breathers in principle possible with the proposed dynamical procedures.Comment: 19 pages, 14 figures, Invited (Review) Chapte

Resonance optimization of polychromatic light in disordered structures

Disorder offers rich possibilities for manipulating the phase and intensity of light and designing photonic devices for various applications including random lasers, light storage, and speckle-free imaging. Disorder-based optical systems can be implemented in one-dimensional structures based on random or pseudo-random alternating layers with different refractive indices. Such structures can be treated as sequences of scatterers, in which spatial light localization is characterized by random sets of spectral transmission resonances, each accompanied by a relatively high-intensity concentration. The control and manipulation of resonances is the key element in designing disorder-based photonic systems. In this work, we introduce a method of controlling disorder-induced resonances by using the established non-trivial interconnection between the symmetry of bi-directional light propagation properties and the features of the resonant transmissions. Considering a fiber with resonant Bragg gratings as an example, the mechanism of enhancing or suppressing the resonant transmission of polychromatic light and the effectiveness of the method have been demonstrated both theoretically and experimentally. The proposed algorithm of controlling disorder-induced resonances is general and applicable to classical waves and quantum particles, for disordered systems both with and without gain

Spatially oriented plasmonic ‘nanograter’ structures

One of the key motivations in producing 3D structures has always been the realization of metamaterials with effective constituent properties that can be tuned in all propagation directions at various frequencies. Here, we report the investigation of spatially oriented “Nanograter” structures with orientation-dependent responses over a wide spectrum by focused-ion-beam based patterning and folding of thin film nanostructures. Au nano units of different shapes, standing along specifically designated orientations, were fabricated. Experimental measurements and simulation results show that such structures offer an additional degree of freedom for adjusting optical properties with the angle of inclination, in additional to the size of the structures. The response frequency can be varied in a wide range (8 μm–14 μm) by the spatial orientation (0°–180°) of the structures, transforming the response from magnetic into electric coupling. This may open up prospects for the fabrication of 3D nanostructures as optical interconnects, focusing elements and logic elements, moving toward the realization of 3D optical circuits

Testing CPT- and Lorentz-odd electrodynamics with waveguides

We study CPT- and Lorentz-odd electrodynamics described by the Standard Model Extension. Its radiation is confined to the geometry of hollow conductor waveguide, open along $z$. In a special class of reference frames, with vanishing both 0-th and $z$ components of the background field, $(k_{\rm AF})^\mu$, we realize a number of {\em huge and macroscopically detectable} effects on the confined waves spectra, compared to standard results. Particularly, if $(k_{\rm AF})^\mu$ points along $x$ (or $y$) direction only transverse electric modes, with $E_z=0$, should be observed propagating throughout the guide, while all the transverse magnetic, $B_z=0$, are absent. Such a strong mode suppression makes waveguides quite suitable to probe these symmetry violations using a simple and easily reproducible apparatus.Comment: 11pages, double-spacing, tex forma

Colloquium: Nonlinear metamaterials

© 2014 American Physical Society. This Colloquium presents an overview of the research on nonlinear electromagnetic metamaterials. The developed theoretical approaches and experimental designs are summarized, along with a systematic description of various phenomena available with nonlinear metamaterials

All-Dielectric Multilayer Cylindrical Structures for Invisibility Cloaking

We study optical response of all-dielectric multilayer structures and demonstrate that the total scattering of such structures can be suppressed leading to optimal invisibility cloaking. We use experimental material data and a genetic algorithm to reduce the total scattering by adjusting the material and thickness of various layers for several types of dielectric cores at telecommunication wavelengths. Our approach demonstrates 80-fold suppression of the total scattering cross-section by employing just a few dielectric layers