Nonlinear chaotic dynamics in nonlocal plasmonic core-shell nanoparticle dimer

Temporal dynamics of surface phonon polaritons in polar dielectric nanoparticles with nonlocality

Surface phonon polaritons (SPhPs) supported by polar dielectrics have been a promising platform for nanophotonics in mid-infrared spectral range. In this work, the temporal dynamic behavior of polar dielectric nanoparticles without (or with) spatial dispersion/nonlocality driven by the ultrashort Gaussian pulses is carried out. We demonstrate that three possible scenarios for the temporal evolutions of the dipole moment including ultrafast oscillations with the decay, exponential decay, and keeping a Gaussian shape exist, when the pulse duration of the incident field is much shorter than, similar to, and much longer than the localized SPhP lifetime. Once the nonlocal effect is considered, the oscillation period becomes large slightly, and the exponential decay turns fast. Furthermore, nonlocality-induced novel temporal behavior is found such as the decay with long-period oscillations when the center frequency of the incident pulse lies at the frequency of adjacent longitudinal resonant modes. The positive and negative time-shifts of the dielectric response reveal that the excitation of the dipole moment will be delayed or advanced. These temporal evolutions can pave the way towards potential applications in the modulation of ultrafast signals for the mid-infrared optoelectronic nanodevices.

Gap-enhanced optical bistability in plasmonic core-nonlinear shell dimers

Localized surface plasmon resonance in capacitively-coupled metallic nanoparticle dimers accompanied by a substantial local field enhancement in the interparticle gap area can enable boosting of nonlinear optical effects. In this paper, we analyze optical bistability in a plasmonic spherical dimer wrapped by a mutual nonlinear shell. In the common graphical post-processing technique of optical bistability, it is assumed that the refractive index change is homogeneous throughout the whole shell. However, we resolve this issue by taking into account the inhomogeneous nature of the power density in the dimer and linking the refractive index change to the local intensity inside the shell. The hysteresis branches of the normalized scattering and extinction cross-sections, as well as electric near-field strength, were derived by increasing and decreasing the driving field intensity. The analysis shows that optical bistability in the dimer with a 3 nm gap can be achieved at switching intensities of about 375 kW cm-2 and 225 kW cm-2, where each stable state of the C-Sh dimer corresponds to a certain plasmonic mode. The range of driving field intensities can be further decreased by considering smaller interparticle distances. The influence of the nonlinear shell on the spectral response is also examined. Suggested configurations distributed on a planar dielectric substrate have potential applications as all-optical switches and memory elements.