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The original Kerker effect was introduced for a hypothetical magnetic sphere, and initially it did not attract much attention due to a lack of magnetic materials required. Rejuvenated by the recent explosive development of the field of metamaterials and especially its core concept of optically-induced artificial magnetism, the Kerker effect has gained an unprecedented impetus and rapidly pervaded different branches of nanophotonics. At the same time, the concept behind the effect itself has also been significantly expanded and generalized. Here we review the physics and various manifestations of the generalized Kerker effects, including the progress in the emerging field of meta-optics that focuses on interferences of electromagnetic multipoles of different orders and origins. We discuss not only the scattering by individual particles and particle clusters, but also the manipulation of reflection, transmission, diffraction, and absorption for metalattices and metasurfaces, revealing how various optical phenomena observed recently are all ubiquitously related to the Kerker's concept.

Nonreciprocity and one-way propagation of optical signals is crucial for modern nanophotonic technology, and is typically achieved using magneto-optical effects requiring large magnetic biases. Here we suggest a fundamentally novel approach to achieve unidirectional propagation of surface plasmon-polaritons (SPPs) at metal-dielectric interfaces. We employ a direct electric current in metals, which produces a Doppler frequency shift of SPPs due to the uniform drift of electrons. This tilts the SPP dispersion, enabling one-way propagation, as well as zero and negative group velocities. The results are demonstrated for planar interfaces and cylindrical nanowire waveguides., Comment: 4 pages, 4 figures, to appear in Opt. Lett

In nanophotonics, subwavelength localization of light is usually associated with plasmonics, the collective excitation of electrons and electromagnetic waves at metallic surfaces. Recent developments in the physics of high-index dielectric nanoparticles, however, suggest an alternative mechanism of light localization: low-order dipole and higherorder multipole Mie resonances. These resonances can generate a strong magnetic response that can be leveraged in designing metasurfaces with unidirectional scattering, as well as efficient metadevices. Indeed, as the power of this approach becomes increasingly apparent, high-index nanomaterials could complement, or even substitute for, plasmonic materials in a range of devices—and could spur a new era in nonlinear nanophotonics.

We demonstrate transparent metaholograms based on silicon metasurfaces that allow high-resolution grayscale images to be encoded. The holograms feature the highest diffraction and transmission efficiencies, and operate over a broad spectral range.

Nonlinear nanophotonics is a rapidly developing field with many useful applications for a design of nonlinear nanoantennas, light sources, nanolasers, sensors, and ultrafast miniature metadevices. A tight confinement of the local electromagnetic fields in resonant photonic nanostructures can boost nonlinear optical effects, thus offering versatile opportunities for subwavelength control of light. To achieve the desired functionalities, it is essential to gain flexible control over the near- and far-field properties of nanostructures. Thus, both modal and multipolar analyses are widely exploited for engineering nonlinear scattering from resonant nanoscale elements, in particular for enhancing the near-field interaction, tailoring the far-field multipolar interference, and optimization of the radiation directionality. Here, we review the recent advances in this recently emerged research field ranging from metallic structures exhibiting localized plasmonic resonances to hybrid metal-dielectric and all-dielectric nanostructures driven by Mie-type multipolar resonances and optically-induced magnetic response., Comment: 17 pages, 6 figures

We demonstrate the enhancement of magnetic dipole spontaneous emission from Eusup3+/supions by an engineered plasmonic nanostructure that controls the electromagnetic environment of the emitter. Using an optical microscope setup, an enhancement in the intensity of the Eusup3+/supmagnetic dipole emission was observed for emitters located in close vicinity to a gold nanohole array designed to support plasmonic resonances overlapping with the emission spectrum of the ions.

We reveal that the resonant Mie scattering by high-index dielectric nanoparticles can be presented through cascades of Fano resonances. We employ the exact solution of Maxwell's equations and demonstrate that the Lorenz-Mie coefficients of the Mie problem can be expressed generically as infinite series of Fano functions as they describe interference between the background radiation originated from an incident wave and narrow-spectrum Mie scattering modes that lead to Fano resonances.

We demonstrate that optically driven two-dimensional lattices of nonlinear metal nanoparticles can support a variety of dissipative localized modes including Faraday ripples, trapped and walking solitons, oscillons, and switching waves connecting different polarization states.

This special issue presents a cross-section of recent progress in the rapidly developing area of optics of hyperbolic metamaterials. © 2013 Optical Society of America.

We show that the simple interaction of spatial optical solitons in nematic liquid crystals with dielectric particles preserves in most cases the self-confinement of these robust nonlinear self-trapped beams, also known as nematicons. Employing spherical defects such as air bubbles and glass spheres, we report on the experimental observation of total internal reflection as well as refractive deflection of nematicons, with angular changes as large as nearly 90°. We also show multiple reflections and the interaction of a particle with two counterpropagating nematicons.

We study scattering of light from multi-layer plasmonic nanowires and reveal that such structures can demonstrate both enhanced and suppressed scattering regimes. We employ the mode-expansion method and experimental data for material parameters and introduce an optimized core-shell nanowire design which exhibits simultaneously superscatter-ing and cloaking properties at different wavelengths in the visible spectrum.

We study the optical response of a metamaterial surface created by a lattice of split-ring resonators covered with a nematic liquid crystal and demonstrate millisecond timescale switching between electric and magnetic resonances of the metasurface. This is achieved due to a high sensitivity of liquid-crystal molecular reorientation to the symmetry of the metasurface as well as to the presence of a bias electric field. Our experiments are complemented by numerical simulations of the liquid-crystal reorientation., Comment: 6 pages, 3 figures

We demonstrate that an interplay between diffraction and defocusing nonlinearity can support stable self-similar plasmonic waves with a parabolic profile. Simplicity of a parabolic shape combined with the corresponding parabolic spatial phase distribution creates opportunities for controllable manipulation of plasmons through a combined action of diffraction and nonlinearity.

We theoretically study the cascaded four-wave mixing (FWM) in broadband tapered plasmonic nanoantennas. In comparison with nonlinear bulk medium they demonstrate a 300-fold increase in nonlinear frequency conversion detected in the main lobe of the nanoantenna far-field pattern. This is achieved by tuning the elements of the nanoantenna to resonance frequencies involved in the FWM interaction. Our findings have a potentially broad application in ultrafast nonlinear spectroscopy, sensing, on-chip optical frequency conversion, nonlinear optical metamaterials, and photon sources.

A split-ring resonator (SRR) is an inductive metallic ring with a gap that can support an oscillating current, giving rise to an optically induced magnetic moment. Unfortunately, metal intrinsic loss sets the limit for using SRRs at optical frequencies. But according to our work, spherical silicon nanoparticles can make an attractive alternative.

We introduce the concept of a nanoradar based on the operation of a nonlinear plasmonic nanoantenna. The nanoradar action originates from modulational instability occurred in a dimer nanoantenna consisting of two subwavelength nonlinear nanoparticles. Modulation instability causes a dynamical energy exchange between the nanoantenna eigenmodes resulting in periodic scanning of the nanoantenna scattering pattern. Such nanoradar demonstrates a wide scanning sector, low operation threshold, and ultrafast time response being potentially useful for many applications in nanophotonics circuitry., 3 pages, 4 figures, Opt. Lett., accepted

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.

We demonstrate that light propagation in waveguide arrays that include PT-symmetric structures can exhibit strongly nonlocal sensitivity to topology of the array at fixed other parameters. We consider an array composed of lossless waveguides, that includes a pair of PT-symmetric waveguides with balanced gain and loss, and reveal that PT-symmetry breaking thresholds are different for planar and circular array configurations. These results demonstrate that PT-symmetric structures can offer new regimes for optical beam shaping compared to conservative structures.

We suggest and demonstrate numerically that, by employing tapered waveguides in the geometry of a directional coupler, we can enhance dramatically the performance for optical switching of nonlinear plasmonic couplers operating at the nanoscale, overcoming the detrimental losses but preserving the subwavelength confinement. We demonstrate that, by an appropriate choice of the taper angle of the coupled metal-dielectric slot waveguides, we can compensate for the amplitude decrease and enhance the sharpness of the response for the switching operation.

This letter reports the first experimental observation, to our knowledge, of optical vector solitons composed of two incoherently coupled vortex components. We employ nematic liquid crystal to generate stable vector solitons with counterrotating vortices and hidden vorticity. In contrast, the solitons with explicit vorticity and corotating vortex components show azimuthal splitting.

We study experimentally and numerically the dynamics of a recently found topological phase transition for discrete quadratic solitons with linearly coupled SH waves. We find that, although no stationary states are excited in the experimental situation, the generic feature of the phase transition of the SH is preserved. By utilizing simulations of the coupled mode equations we identify the complex processes leading to the phase transition involving spatial focusing and the generation of new frequency components. These distinct signatures of the dynamic phase transition are also demonstrated experimentally.

We demonstrate the fabrication by direct laser writing and the operation of a directional coupler containing Bragg gratings in each waveguide. We achieve high-precision control over the longitudinal shift between the gratings, which feature first-order Bragg resonance at telecommunication wavelengths. We observe fundamental differences between light transmission characteristics in couplers with unshifted and shifted gratings in agreement with theoretical predictions.

We develop a systematic approach for simultaneous extraction of the dispersion relations and profiles of multiple modes in periodic waveguides though a special global optimization procedure applied to near-field electric field measurements in the waveguide plane. We apply this method to perform in-depth analysis of experimental data on wave propagation close to an interface between waveguide sections with different dispersion characteristics, and we successfully identify several modes contributing to the experimentally measured fields. We find clear evidence that when the group velocity is reduced across the interface, evanescent modes that facilitate the excitation of propagating slow-light waves appear, confirming previous theoretical predictions. (C) 2011 Optical Society of America Publisher PDF

The use of light for controlling objects led to the development of optical tweezers. Now, the applications have expanded into the creation of three-dimensional structures and the control of surface structures.

We propose and analyze an on-chip all-optical dynamic tuning scheme for coupled nonlinear resonators employing a single control beam injected in parallel with a signal beam. We show that the nonlinear Kerr response can be used to dynamically switch the spectral properties between a "dark state" and electromagnetically induced transparency configurations. Such a scheme can be realized in integrated optical applications for pulse trapping and delaying.

We demonstrate experimentally a transition from nonlinear beam trapping to defocusing in a two-dimensional periodic photonic structures by varying the modulation depth of the lattice. The observed effect illustrates the fundamental crossover from discrete to cw transport mechanisms. At the threshold modulation, the output beam is highly sensitive to refractive index and power variations, which can be potentially applied for high-sensitivity refractive index or temperature sensing.

We study experimentally an electrically pumped GaAs-based bandgap structure based on a vertical cavity surface emitting laser (VCSEL). We demonstrate that a microcavity embedded into this bandgap VCSEL structure supports localized optical modes without any holding beam. We propose a model of surface-structured VCSELs based on a reduced dissipative wave equation for describing electromagnetic modes in such semiconductor cavities and analyze a crossover between linear and nonlinear solitonlike cavity modes.

We theoretically and experimentally study the nonlinear propagation of polychromatic light in curved waveguide arrays. We show that at moderate light powers the nonlinear self-action breaks the left-right symmetry of the polychromatic beam, resulting in the separation of different spectral components owing to the wavelength-dependent spatial shift. At high light powers a diffraction-managed polychromatic soliton is formed. These results demonstrate new possibilities for tunable demultiplexing and spatial filtering of supercontinuum light.

We suggest a new approach for selective trapping of light absorbing particles in gases by multiple optical bottle-beam-like traps created by volume speckle field. We demonstrate stable simultaneous confinement of a few thousand micro-particles in air with a single low-power laser beam. The size distribution of trapped particles exhibits a narrow peak near the average size of an optical speckle. Thus, the speckle-formed traps act as a sieve with the holes selecting particles of a similar size.

We observe experimentally optical azimuthons, a generic class of ring-shaped localised spiralling beams with azimuthal modulation, carrying phase dislocation in self-focusing nonlinear media. We observe three- and four-lobe azimuthons in 87Rb vapours and demonstrate their anomalous rotation controlled by the input phase distribution.

We demonstrate that the spatial profiles of both propagating and evanescent Bloch-modes in a periodic structure can be extracted from a single measurement of electric field at the specified optical wavelength. We develop a systematic extraction procedure by extending the concepts of high-resolution spectral methods previously developed for temporal data series to take into account the symmetry properties of Bloch-modes simultaneously at all spatial locations. We apply our method to a photonic crystal waveguide interface and confirm its robustness in the presence of noise., 3 pages, 3 figures

We study interaction of counterpropagating beams in truncated two-dimensional photonic lattices induced optically in photorefractive crystals, and demonstrate the existence of counterpropagating surface solitons localized in the lattice corners and at the edges. We display intriguing dynamical properties of such composite optical beams and reveal that the lattice surface provides a strong stabilization effect on the beam propagation. We also observe dynamical instabilities for stronger coupling and longer propagation distances in the form of beam splitting. No such instabilities exist in the single beam surface propagation.

We analyze phase matching in metal-dielectric nonlinear structures which support highly localized plasmon polariton modes. We reveal that quadratic phase matching between the plasmon modes of different symmetries becomes possible in planar waveguide geometries. We discuss the example of a nonlinear LiNbO(3) waveguide sandwiched between two silver plates, and demonstrate that second-harmonic generation can be achieved for interacting plasmonic modes.

We analyze stability of the TM polarized optical solitons and nonlinear guided waves localized at a metal-dielectric interface. We demonstrate, both analytically and numerically, that the spatial solitons can experience vectorial transverse modulational instability that leads to the generation of arrays of two-dimensional TM polarized self-trapped localized beams. In a sharp contrast, we reveal that the transverse instability is completely eliminated for nonlinear surface plasmons.

We demonstrate, both theoretically and experimentally, the existence of nonlocal gap solitons in two-dimensional periodic photonic structures with defocusing thermal nonlinearity. We employ liquid-infiltrated photonic crystal fibers and show how the system geometry can modify the effective response of a nonlocal medium and the properties of two-dimensional gap solitons.

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.

We generate experimentally optical bottle beams from incoherent double-charge white-light vortices, and show that their parameters can be efficiently controlled by varying the beam focusing conditions.

Diffractive Structures: Photonic structures began in the search for localization associated with defects. Now, however, localized states have been demonstrated in defect-free media.

Scattering: We have missed the presence of resonant scattering behavior in the Rayleigh region for years, but a clue was lurking in quantum theory.

This work was supported by the Australian Research Council under the Centres of Excellence Program and through the Australian Partnership for Advanced Computing National Facility (APAC). Part of this project was completed during the visit of A. A. Sukhorukov to McMaster University (Canada) supported by the Australian Academy of Science travel grant. D. N. Chigrin acknowledges partial support by the Deutsche Forschungsgemeinschaft (DFG) through the project FOR 557. A. V. Laurinenko acknowledges partial support from European Commission FP6, project NewTon, NMP4-CT-2005- 017160.

We study experimentally the process of the second harmonic generation by two noncollinear beams in quadratic nonlinear crystals with a disordered structure of ferroelectric domains. We show that the second-harmonic radiation is emitted in the form of two cones as well as in a plane representing the cross-correlation of the two fundamental pulses. We demonstrate the implementation of this parametric process for characterisation of femtosecond pulses, enabling the estimation of pulse width, chirp, and front tilt. This is achieved through monitoring the evolution of the autocorrelation trace inside the nonlinear crystal.

We demonstrate experimentally the formation of polychromatic single- and double-charge optical vortex solitons by employing a lithium niobate crystal as a nonlinear medium with defocusing nonlinearity. We study the wavelength dependence of the vortex core localization and observe self-trapping of polychromatic vortices with a bandwidth spanning over more than 70 nm for single-charge and 180 nm for double-charge vortex solitons.

We study nonlinear light propagation in colloidal nanosuspensions. We introduce a novel model for the nonlinear response of colloids which describes consistently the system in the regimes of low and high light intensities and low/large concentrations of colloidal particles. We employ this model to study the light-induced instabilities and demonstrate the formation of stable spatial solitons as well as the existence of a bistability regime.

tonic structures in the form of waveguide arrays. The arrays feature the refractive index modulation in the transverse spatial dimension [see (a)] with the characteristic period of several wavelengths, resembling the periodic cladding of PCFs. In such structures, back-scattering is absent and transmission coefficients can approach unity simultaneously for all spectral components. In addition, the spatial beam propagation in waveguide arrays tends to change smoothly as the optical wavelength is varied by hundreds of nanometers, in contrast to the sharp spectral sensitivity in photonic crystals, where the refractive index is modulated in the propagation direction on wavelength scale. Following the theoretical analysis, 2 we demonstrated spatio-spectral reshaping of supercontinuum light achieved through nonlinear interaction of spectral components in an array of optical waveguides fabricated in a LiNbO 3 crystal. 3,4 At

Phase matching is a necessity, but what happens in the extreme? Can we use the nonlinear processes to create the necessary phase matching?

We demonstrate that a concentric ring coupler can be employed for nonlinear switching of the angular momentum of light carried by an optical vortex. We find different types of stationary vortex states in the nonlinear coupler and study coupling of both power and momentum of an optical vortex launched into one of the rings, demonstrating that the switching takes place well below the collapse threshold. The switching is more effective for the inner-ring excitation since it triggers more sharply and for the powers low enough to avoid the vortex instability and breakup.

We study surface modes in semi-infinite chirped two-dimensional photonic lattices in the frame- work of an effective discrete nonlinear model. We demonstrate that the lattice chirp can change dramatically the conditions for the mode localization near the surface, and we find numerically the families of surface modes, in linear lattices, and discrete surface solitons, in nonlinear lattices. We demonstrate that, in a sharp contrast to one-dimensional discrete surface solitons, in two-dimensional lattices the mode threshold power is lowered by the action of both the surface and lattice chirp. By manipulating with the lattice chirp, we can control the mode position and its localization.

We introduce a novel class of stable lattice solitons with a complex phase structure composed of many single-charge discrete vortices in a triangular photonic lattice. We demonstrate that such nonlinear self-trapped states are linked to the resonant Bloch modes, which bear a honeycomb pattern of phase dislocations.

We study light propagation in arrays of weakly coupled nonlinear cavities driven by an inclined holding beam. We show analytically that both discreteness and inclination of the driving field can dramatically change the conditions for modulational instability in discrete nonlinear systems. We find numerically the families of resting and moving dissipative solitons for an arbitrary inclination angle of the driving field, both in the discrete and a quasi-continuous limits. We analyze a crossover between resting and moving cavity solitons, and also observe novel features in the soliton collision.