Nonlinear Control of Electromagnetic Topological Edge States.

Topological photonics has emerged recently as a smart approach for realizing robust optical circuitry, and the study of nonlinear effects is expected to open the door for tunability of photonic topological states. Here we realize experimentally nonlinearity-induced spectral tuning of electromagnetic topological edge states in arrays of coupled nonlinear resonators in the pump-probe regime. When nonlinearity is weak, we observe that the frequencies of the resonators exhibit spectral shifts concentrated mainly at the edge mode and affecting only weakly the bulk modes.

Nanoscale Generation of White Light for Ultrabroadband Nanospectroscopy.

Achieving efficient localization of white light at the nanoscale is a major challenge due to the diffraction limit, and nanoscale emitters generating light with a broadband spectrum require complicated engineering. Here we suggest a simple, yet highly efficient, nanoscale white-light source based on a hybrid Si/Au nanoparticle with ultrabroadband (1.3-3.

Resonant metasurfaces at oblique incidence: interplay of order and disorder.

Understanding the impact of order and disorder is of fundamental importance to perceive and to appreciate the functionality of modern photonic metasurfaces. Metasurfaces with disordered and amorphous inner arrangements promise to mitigate problems that arise for their counterparts with strictly periodic lattices of elementary unit cells such as, e.g.

Broadband light coupling to dielectric slot waveguides with tapered plasmonic nanoantennas.

We propose and theoretically verify an efficient mechanism of broadband coupling between incident light and on-chip dielectric slot waveguide by employing a tapered plasmonic nanoantenna. The nanoantenna receives free space radiation and couples it to a dielectric slot waveguide with the efficiency of up to 20% in a broad spectral range, having a small footprint as compared with the currently used narrowband dielectric grating couplers. We argue that the frequency selective properties of such nanoantennas also allow for using them as ultrasmall on-chip multiplexer/demultiplexer devices.

Self-localization of polariton condensates in periodic potentials.

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.

Cascaded four-wave mixing in tapered plasmonic nanoantenna.

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.

All-optical switching of a signal by a pair of interacting nematicons.

We investigate a power tunable junction formed by two interacting spatial solitons self-trapped in nematic liquid crystals. By launching a counter-propagating copolarized probe we assess the guided-wave behavior induced by the solitons and demonstrate a novel all-optical switch. Varying soliton power the probe gets trapped into one or two or three guided-waves by the soliton-induced index perturbation, an effect supported by the nonlocal nonlinearity.

Biphoton generation in quadratic waveguide arrays: a classical optical simulation.

Quantum entanglement became essential in understanding the non-locality of quantum mechanics. In optics, this non-locality can be demonstrated on impressively large length scales, as photons travel with the speed of light and interact only weakly with their environment. Spontaneous parametric down-conversion (SPDC) in nonlinear crystals provides an efficient source for entangled photon pairs, so-called biphotons.