Sum frequency generation from touching wires: a transformation optics approach
TL;DR: In this paper, the authors employ transformation optics to study analytically nonlinear wave mixing from a singular geometry of touching plasmonic wires and obtain the analytic solution of the near field and complement it with a solution of far-field properties.
Abstract: We employ transformation optics to study analytically nonlinear wave mixing from a singular geometry of touching plasmonic wires. We obtain the analytic solution of the near field and complement it with a solution of far-field properties. We find, somewhat surprisingly, that optimal efficiency (in both regimes) is obtained for the degenerate case of second-harmonic generation. We exploit the analytic solution obtained to trace this behavior to the spatial overlap of input fields near the geometric singularity.
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TL;DR: In this paper, a complete expression for the intensity and polarization of reflected harmonic radiation as a function of the angle of incidence and state of polarization of the incident laser beam is derived.
Abstract: The radiation at the boundary of an isotropic or cubic medium by a polarization at $2\ensuremath{\omega}$, the amplitude of which is proportional to the product of the incident laser field at $\ensuremath{\omega}$ and a spatial derivative of this field, is examined theoretically. A complete expression for the intensity and polarization of the reflected harmonic radiation as a function of the angle of incidence and state of polarization of the incident laser beam is derived. The angular dependences are in good agreement with observations on Si, Ge, and Ag. Some additional experimental results, not previously reported, are described. The magnitude of the nonlinearity due to bound electrons in these cubic materials is related to the square of the linear susceptibility, and agrees qualitatively with observations in Si, Ge, and alkali halides. This nonlinearity has the same order of magnitude as that caused by conduction electrons in metals, which has been extensively discussed in the literature. The influence of absorbed surface layers is considered.
567 citations
TL;DR: In this paper, the second-harmonic generation of light at metal surfaces within the hydrodynamic theory of the electron gas is discussed, and expressions for the phenomenological parameters $a$ and $b$ of Rudnick and Stern are presented.
Abstract: We discuss the second-harmonic generation of light at metal surfaces within the hydrodynamic theory of the electron gas; expressions for the phenomenological parameters $a$ and $b$ of Rudnick and Stern are presented, and the possibility of a resonance in $a$ at optical or near-uv frequencies is discussed. A recent plasmon-enhanced experiment of Simon et al. is analyzed, and the use of such experiments to determine $a$ and $b$ is considered; new experiments are proposed to aid in such a determination.
294 citations
TL;DR: In this paper, the second-harmonic radiation generated by the reflection of incident radiation from a metal surface in a model that considers only plasma effects and neglects periodic lattice structure in the metallic bulk and any form of surface roughness was performed.
Abstract: A calculation is performed of the second-harmonic radiation generated by the reflection of incident radiation from a metal surface in a model that considers only plasma effects and neglects periodic lattice structure in the metallic bulk and any form of surface roughness. The radiation is due to three kinds of currents: one localized to within a few angstroms of the surface and parallel to it, another also localized at the surface but normal to it, and a bulk current in the skin-depth region of the incident light, a region several hundred angstroms thick. Previous expressions for the normal surface current are found to be incorrect, and a new expression is derived. The second-harmonic radiation due to the surface currents is sensitive to surface conditions, while the contribution of the bulk current is only weakly sensitive to them. Theoretical estimates suggest that changes in the radiation intensity with variation in surface condition are caused primarily by changes in the parallel surface currents due to variations in surface scattering. In the course of this investigation general relationships and explicit forms for the second-order response of an isotropic electron gas are given.
245 citations
TL;DR: An insightful transformation-optics approach is developed to investigate the impact that nonlocality has on the optical properties of plasmonic nanostructures and elucidate the optimum size that maximizes its absorption and field enhancement capabilities.
Abstract: We develop an insightful transformation-optics approach to investigate the impact that nonlocality has on the optical properties of plasmonic nanostructures. The light-harvesting performance of a dimer of touching nanowires is studied by using the hydrodynamical Drude model, which reveals nonlocal resonances not predicted by previous local calculations. Our method clarifies the interplay between radiative and nonlocal effects in this nanoparticle configuration, which enables us to elucidate the optimum size that maximizes its absorption and field enhancement capabilities.
212 citations
TL;DR: In this article, the second-harmonic generation of 150 nm spherical gold nanoparticles is investigated both experimentally and theoretically, and the interference effects between dipolar and octupolar plasmons can be used as a fingerprint to discriminate the local surface and nonlocal bulk contributions to the second harmonic generation.
Abstract: The second-harmonic generation of 150 nm spherical gold nanoparticles is investigated both experimentally and theoretically. We demonstrate that the interference effects between dipolar and octupolar plasmons can be used as a fingerprint to discriminate the local surface and nonlocal bulk contributions to the second-harmonic generation. By fitting the experimental data with the electric fields computed with finite-element method simulations, the Rudnick and Stern parameters weighting the relative nonlinear sources efficiencies are evaluated and the validity of the hydrodynamic model and the local density approximation approaches are discussed.
197 citations