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We numerically study second harmonic generation from plasmonic nanotubes of air-core and ultrathin gold shell using classical nonlocal hydrodynamic model of free electron. We demonstrate that the nonlocal effect of gold significantly affects the linear optical response and second harmonic generation in such ultrathin nanotubes with shell down to a few nanometers or subnanometer scale, comparing with the conventional local Drude model of gold. We specially emphasize second harmonic generation from the nanotube structures of dipole plasmon resonance at fundamental wavelength and dipole/quadrupole resonance at second harmonic wavelength. Our results indicate that, the output of second harmonic generation is dominantly enhanced by the dipole plasmon resonance at fundamental wavelength via the strong local electric field and also can be significantly enhanced by dipole- and quadrupole-resonant scattering at second harmonic wavelength. The nonlinear sources of second harmonic generation in ultrathin gold nanotubes, including nonlinear Coulomb interaction, convective term, Lorentz force, and nonlinear pressure are studied separately, and the dominant contributions from convective term and nonlinear Coulomb term are reported. [ABSTRACT FROM AUTHOR]

Abstract: Similar to the treatment of self-propelled particles, a generalized car following model with multiple look-ahead was utilized for the study of vehicular traffic. With the assumption of no skewness in velocity distribution and through iterative procedure, it is possible to construct a second order nonlocal hydrodynamic model. In contrast with two-phase fluid-dynamic models with a fundamental diagram, the model has the advantage of microscopically determined relaxation time parameters. Although the rigor is reduced a little compared with the Navier–Stokes like traffic flow model previously studied, the phase transition from free flow to synchronized flow, then from synchronized flow to wide moving jam is reproduced. The catch effect of synchronized flow is also revealed. The simulations suggest that the nonlocality in relaxation time and steady velocity, even though without nonlocality in viscocity, i.e., velocity variance, gives another explanation of synchronized flow. [Copyright &y& Elsevier]

In order to model the interaction between light and plasmonic structures at deep-nanometer scale, which is governed by non-classical effects, a nonlocal hydrodynamic approach has been extensively studied. Several hydrodynamic models have been proposed, solving the coupled equations: the linearized hydrodynamic equation of motion and the electrodynamic Maxwell’s equations, by employing additional boundary conditions. This work compares four hydrodynamic models: the hard wall hydrodynamic model (HW-HDM), the curl-free hydrodynamic model (CF-HDM), the shear forces hydrodynamic model (SF-HDM), and the quantum hydrodynamic model (Q-HDM). The analysis is conducted for a metallic spherical nanoparticle, as an example. The above hydrodynamic models are also compared with experiments available in literature. It is demonstrated that HW-HDM and QHDM outperform the other two hydrodynamic models. [ABSTRACT FROM AUTHOR]

Many computational methods have been developed and used for modeling, understanding, and tailoring extreme optical effects at the nanoscale. Among them, this review focuses on the integral equation‐based methods: within the local response limit, a potential‐based boundary integral equation (BIE) formalism and a field‐based volume integral equation (VIE) formalism; within the nonlocal hydrodynamic model, a potential‐based BIE formalism. These formalisms are derived from macroscopic electrodynamics (together with appropriate constitutive relations). The derivations are based on three pillars: the Green function, the field relation(s) (for the VIE formalism, the incident—scattered—total field relation; for the BIE formalism, the interface conditions connecting the fields at two sides of the interface), and the field equivalence principle (for the VIE formalism, the volume equivalence principle; for the BIE formalism, the Huygens principle). By applying the method of moments (MoM) algorithm, the derived integral equations are converted into matrix equations, with possible problems in the implementation being discussed. Levels of solutions, including the eigenmode and natural mode solutions, and group representation theory are introduced as powerful post‐processing steps. Many examples are shown to demonstrate the effectiveness of the reviewed algorithms. [ABSTRACT FROM AUTHOR]