The field of optical nanoantennas, a rapidly developing area of optics, is reviewed. The basic concept of an optical antenna is formulated and major characteristics relevant to this structure are identified. A classification of nanoantennas into metallic and dielectric (the latter including semiconductor nanoantennas) is made. For either category, the literature is reviewed and strengths and weaknesses of different approaches are discussed. The basics of nonlinear optical antennas are outlined. Future avenues of research and application areas for the field are highlighted, and its prospects are examined.

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Topological photonics has recently emerged as a route to realize robust optical circuitry, and nonlinear effects are expected to enable tunability of topological states with the light intensity. Here we realize experimentally nonlinear self-induced spectral tuning of the electromagnetic topological edge states in an array of coupled nonlinear resonators in a pump-probe experiment. In a weakly nonlinear regime, we observe that resonators frequencies exhibit spectral shifts, that are concentrated mainly at the edge mode affecting only weakly the bulk modes. For a strong pumping, we describe several scenarios of the transformation of the edge states and their hybridization with bulk modes, and also predict a parametrically driven transition from topological to unstable regimes.

We predict the existence of novel spatially localized states of exciton-polariton Bose-Einstein condensates in semiconductor microcavities with fabricated periodic in-plane potentials. Our theory shows that, under the conditions of continuous nonresonant pumping, localization is observed for a wide range of optical pump parameters due to effective potentials self-induced by the polariton flows in the spatially periodic system. We reveal that the self-localization of exciton-polaritons in the lattice may occur both in the gaps and bands of the single-particle linear spectrum, and is dominated by the effects of gain and dissipation rather than the structured potential, in sharp contrast to the conservative condensates of ultracold alkali atoms.

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We introduce a novel hybrid metal-dielectric nanoantenna composed of dielectric (crystalline silicon) and metal (silver) nanoparticles. In such a nanoantenna, the phase shift between the dipole moments of the nanoparticles, caused by differences in the polarizabilities, allows for directional light scattering; while the nonlinearity of the metal nanoparticle helps to control the radiation direction. We show that the radiation pattern of this nanoantenna can be switched between the forward and backward directions by varying only the light intensity around the level of 6 MW cm −2 , with a characteristic switching time of 40 fs.

The scattering of a non linear wave packet as an envelope soli ton by a one-dimensional disordered system is studied. It is well known that in the linear limit the transmission coefficient decays exponentially with a characteristic localization length. We predict, using a simple independent scattering approach and soliton perturbation theory in the framework of the non linear Schrodinger equation, that strong nonlinearity above a certain threshold allows undistorted propagation of wave packets.

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