We investigate the self-trapping phenomenon in one-dimensional nonlinear waveguide arrays. We discuss various approximate analytical descriptions of the discrete self-trapped solutions. We analyze the packing, steering, and collision properties of these solutions, by means of a variational approach and soliton perturbation theory. We compare the analytical and numerical results

Two-dimensional transition-metal dichalcogenides (TMDCs) with intrinsically broken crystal inversion symmetry and large second-order nonlinear responses have shown great promise for future nonlinear light sources. However, the sub-nanometer monolayer thickness of such materials limits the length of their nonlinear interaction with light. Here, we experimentally demonstrate the enhancement of the second-harmonic generation from monolayer MoSe2 by its integration onto a 220-nm-thick silicon waveguide. Such on-chip integration allows for a marked increase in the interaction length between the MoSe2 and the waveguide mode, further enabling phase matching of the nonlinear process. The demonstrated TMDC–silicon photonic hybrid integration opens the door to second-order nonlinear effects within the silicon photonic platform, including efficient frequency conversion, parametric amplification and the generation of entangled photon pairs.

Optical nanoantennas have shown a great capacity for efficient extraction of photons from the near to the far-field, enabling directional emission from nanoscale single-photon sources. However, their potential for the generation and extraction of multi-photon quantum states remains unexplored. Here we demonstrate experimentally the nanoscale generation of two-photon quantum states at telecommunication wavelengths based on spontaneous parametric down-conversion in an optical nanoantenna. The antenna is a crystalline Al-GaAs nanocylinder, possessing Mie-type resonances at both the pump and the bi-photon wavelengths and when excited by a pump beam generates photonpairs with a rate of 35 Hz. Normalized to the pump energy stored by the nanoantenna, this rate corresponds to 1.4 GHz/Wm, being one order of magnitude higher than conventional on-chip or bulk photon-pair sources. Our experiments open the way for multiplexing several antennas for coherent generation of multi-photon quantum states with complex spatial-mode entanglement and applications in free-space quantum communications and sensing.

We demonstrate that nonlinear optical fiber arrays can support stable solitonlike pulses with finite energy. The bound state that we have found is localized both in time and in spatial domain in the direction perpendicular to the pulse propagation. Numerical studies support our analytical conclusions.

Recent progress in nanoscale optics is driven by the physics of electric and magnetic resonances supported by high-index dielectric nanoparticles. Here, we exploit optical bound states in the continuum in a subwavelength particle enhanced by an engineered substrate undergoing an epsilon-near-zero transition from an insulator to a conductor, and uncover how to boost dramatically high-order parametric nonlinear effects. Our strategy makes feasible an observation of a variety of multistep cascaded and multifrequency nonlinear effects in an individual subwavelength resonator. This would expand substantially the range of applications of Mieresonant dielectric metaphotonics for highly efficient subwavelength optical circuitry, nonlinear metadevices, ultrasensitive hyperspectral sensing, and quantum nanophotonics.