Oscillons, solitons, and domain walls in arrays of nonlinear plasmonic nanoparticles

Optical Bistability in Nanosilicon with Record Low Q-Factor

We demonstrated optical bistability in an amorphous silicon Mie resonator with a size of ∼100 nm and Q-factor as low as ∼4 by utilizing photothermal and thermo-optical effects. We not only experimentally confirmed the steep intensity transition and the hysteresis in the scattering response from silicon nanocuboids but also established a physical model to numerically explain the underlying mechanism based on temperature-dependent competition between photothermal heating and heat dissipation. The transition between the bistable states offered particularly steep superlinearity of scattering intensity, reaching an effective nonlinearity order of ∼100th power over excitation intensity, leading to the potential of advanced optical switching devices and super-resolution microscopy.

Soliton-like surface plasmon polaritons generated on the surface of a silver nanowire embedded in a Kerr nonlinear medium

The behavior of surface plasmon polaritons (SPPs) generated on the surface of a silver nanowire by coaxial Gaussian beams in Kerr nonlinear mediums is studied numerically. Enhancement of the propagation of the SPPs is realized due to the introduction of the nonlinear effect. Further adjusting the nonlinearity or the beam's intensity results in a soliton-like propagation of SPPs. This can be explained by the nonlinear self-focusing effect transferring more light into SPP modes and counteracting the attenuation caused by the absorption of metal. This result may contribute to SPP-based applications where an enhanced propagation length is needed.

Anderson localization in metallic nanoparticle arrays

Anderson localization has been observed in various types of waves, such as matter waves, optical waves and acoustic waves. Here we reveal that the effect of Anderson localization can be also induced in metallic nonlinear nanoparticle arrays excited by a random electrically driving field. We find that the dipole-induced nonlinearity results in ballistic expansion of dipole intensity during evolution; while the randomness of the external driving field can suppress such an expansion. Increasing the strength of randomness above the threshold value, a localized pattern of dipole intensity can be generated in the metallic nanoparticle arrays. By means of statistics, the mean intensity distribution of the dipoles reveals the formation of Anderson localization. We further show that the generated Anderson localization is highly confined, with its size down to the scale of incident wavelength. The reported results might facilitate the manipulations of electromagnetic fields in the scale of wavelength.

Effective nonlinear optical properties and optical bistability in composite media containing spherical particles with different sizes

We study the effective nonlinear optical properties of composite media in which identical nonlinear nanospheres are randomly embedded in the linear host medium. In the weakly-nonlinear case, we aim at the effective linear permittivity and effective third-order nonlinear susceptibility with effective medium theory combined with the linear Mie theory. We show that large enhancement of optical nonlinear susceptibility can be achieved at the surface plasmon resonant wavelength, which can be tuned by changing the size of nanoparticles. Our numerical results are compared with those in the quasistatic limit or/and from Comsol simulations, good agreement is found. In the strong-nonlinear case, based on nonlinear Mie theory and self-consistent mean-field method, we study the optical bistability of the composite media. The optical bistability and tristability are found, and the bistable threshold fields are found to be strongly dependent on the sizes of nanoparticles and the incident wavelength. Such nonlinear nanocomposites with large optical nonlinearity and tunable bistable behavior are envisioned for use as nonlinear optical nanodevices such as optical nanoswitches, optical nanomemories and so on.

Plasmonic kinks and walking solitons in nonlinear lattices of metal nanoparticles

We study nonlinear effects in one-dimensional (1D) arrays and two-dimensional (2D) lattices composed of metallic nanoparticles with the nonlinear Kerr-like response and an external driving field. We demonstrate the existence of families of moving solitons in 1D arrays and characterize their properties such as an average drifting velocity. We also analyse the impact of varying external field intensity and frequency on the structure and dynamics of kinks in 2D lattices. In particular, we identify the kinks with positive, negative and zero velocity as well as breathing kinks with a self-oscillating profile.

Coupling of a dipolar emitter into one-dimensional surface plasmon

Quantum plasmonics relies on a new paradigm for light-matter interaction. It benefits from strong confinement of surface plasmon polaritons (SPP) that ensures efficient coupling at a deep subwavelength scale, instead of working with a long lifetime cavity polariton that increases the duration of interaction. The large bandwidth and the strong confinement of one dimensional SPP enable controlled manipulation of a nearby quantum emitter. This paves the way to ultrafast nanooptical devices. However, the large SPP bandwidth originates from strong losses so that a clear understanding of the coupling process is needed. In this report, we investigate in details the coupling between a single emitter and a plasmonic nanowire, but also SPP mediated coupling between two emitters. We notably clarify the role of losses in the Purcell factor, unavoidable to achieve nanoscale confinement down to 10(-4)(λ/n)(3). Both the retarded and band-edge quasi-static regimes are discussed.

Subwavelength solitons and Faraday waves in two-dimensional lattices of metal nanoparticles

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.

Augmenting second harmonic generation using Fano resonances in plasmonic systems

Significant augmentation of second harmonic generation using Fano resonances in plasmonic heptamers made of silver is theoretically and experimentally demonstrated. The geometry is engineered to simultaneously produce a Fano resonance at the fundamental wavelength, resulting in a strong localization of the fundamental field close to the system, and a higher order scattering peak at the second harmonic wavelength. These results illustrate the versatility of Fano resonant structures to engineer specific optical responses both in the linear and nonlinear regimes thus paving the way for future investigations on the role of dark modes in nonlinear and quantum optics.