Efficient Third Harmonic Generation from Metal–Dielectric Hybrid Nanoantennas

Abstract

High refractive index dielectric nanoantennas are expected to become key elements for nonlinear nano-optics applications due to their large nonlinearities, low energy losses, and ability to produce high electric field enhancements in relatively large nanoscale volumes. In this work, we show that the nonlinear response from a high-index dielectric nanoantenna can be significantly improved by adding a metallic component to build a metal-dielectric hybrid nanostructure. We demonstrate that the plasmonic resonance of a Au nanoring can boost the anapole mode supported by a Si nanodisk, strongly enhancing the electric field inside the large third-order susceptibility dielectric. As a result, a high third harmonic conversion efficiency, which reaches 0.007% at a third harmonic wavelength of 440 nm, is obtained. In addition, by suitably modifying geometrical parameters of the hybrid nanoantenna, we tune the enhanced third harmonic emission throughout the optical regime. Coupling metallic and dielectric nanoantennas to expand the potential of subwavelength structures opens new paths for efficient nonlinear optical effects in the visible range on the nanoscale.

Metal–dielectric hybrid nanoantennas for efficient frequency conversion at the anapole mode

“…In this work, by exploiting the plasmonic ring, we obtain a 20-fold increase in the field intensity enhancement averaged over the whole structure volume, F , as compared to the bare nanopillar (see Fig. 3), which is comparable to what was already reported in [37]. …”

“…A further viable strategy involving coupled nanosystems, consists in placing a metal nanostructure in the proximity of the dielectric nanoantenna to manipulate the in- and out-coupling of light [34–35]. This hybrid integration was exploited to significantly boost the nonlinear conversion efficiency of nanosystems [32,36–37]. In particular, Maier and co-workers proposed a nanoantenna composed of a silicon disk core surrounded by an annular plasmonic antenna, which combines the energy-storage capabilities of the anapole mode with the enhanced efficiency of light-coupling in metal–dielectric systems.…”

“…In particular, Maier and co-workers proposed a nanoantenna composed of a silicon disk core surrounded by an annular plasmonic antenna, which combines the energy-storage capabilities of the anapole mode with the enhanced efficiency of light-coupling in metal–dielectric systems. This allowed them to achieve a THG efficiency enhancement up to three orders of magnitude with respect to the bare disk [37]. In this work, we apply the same approach to obtain SHG enhancement in AlGaAs nanostructures [27–28 33] and investigate the properties of the emitted nonlinear optical signal.…”

Nonlinear spectroscopy of plasmonic nanoparticles

“…Several efforts have been undertaken in this direction, both experimentally as well as theoretically, and the subject is still under debate [69,[83][84][85][86][87][88][89][90][91]. One example is shown in Figure 8.…”

“…On resonance, the field is concentrated in the silicon part, which has a nonlinear susceptibility χ (3) that is about an order of magnitude larger than that of gold [64]. Reprinted with permission from [83]. Copyright 2017 American Chemical Society.…”