Second-harmonic generation in hyperbolic plasmonic nanorod metamaterials

摘要

In this talk, we numerically demonstrate the potential of a hyperbolic medium in the design of an efficient metamaterial antenna enhancing the second harmonic generation of a nano-object, with an otherwise hidden nonlinear signature through a metamaterial-assisted access to evanescent second-harmonic fields. In further discussion, we consider the second harmonic generation from the metamaterial itself and report the criterion of its efficiency. Nonlinear optics has always the selected niche in optical science and, in some sense, propelled its evolution, yielding new discoveries and variety of applications. Nano-optics is a very promising approach to achieve efficient nonlinear interactions, since it enables to manipulate electromagnetic modes in the near-field. One of the approaches for this control relies on surface plasmon polaritons (SPPs) excitations in metallic nanostructures and is presently under extensive research. Hyperbolic metamaterials, produced, e.g., by arrays of vertically-oriented metallic nanorods have recently attracted significant attention due to their unusual electromagnetic properties. Homogenized hyperbolic metamaterials were theoretically shown to provide infinitely large LDOS and, as a result, can be expected to facilitate second harmonic generation process. Here, we propose an efficient metamaterial antenna operating in the hyperbolic dispersion regime as a novel approach for nonlinear optical microscopy providing access to evanescent, dark SH fields and converting them into propagating SH light. A 103-fold enhancement of the second harmonic signal from a spherical nonlinear nanoparticle embedded in the metamaterial antenna has been demonstrated. The far-field SH radiation pattern of the nanoparticle was shown to be extremely sensitive to the position of the nanoparticle within the nanorod meta-antenna. In the second part of the talk, we consider intrinsic second-harmonic generation processes in plasmonic nanorod metamaterial itself and show its enhancement at multiple resonant wavelengths determined by the mode structure of the metamaterial at both fundamental and second-harmonic frequencies.