Enhanced Third Harmonic Generation in Single Germanium Nanodisks Excited at the Anapole Mode

Abstract

ABSTRACT. We present an all-dielectric germanium nanosystem exhibiting a strong third order nonlinear response and efficient third harmonic generation in the optical regime. A thin germanium nanodisk shows a pronounced valley in its scattering cross section close to the dark anapole mode, while the electric field energy inside the disk is maximized due to high confinement within the dielectric. We investigate the dependence of the third harmonic signal on disk size and pump wavelength to reveal the nature of the anapole mode. Each germanium nanodisk generates a high effective third order susceptibility of (3) = 4.3 10 −9, corresponding to an associated third harmonic conversion efficiency of 0.0001% at a wavelength of 1650 nm, which is four orders of magnitude greater than the case of an unstructured germanium reference film. Furthermore, the nonlinear conversion via the anapole mode outperforms that via the radiative dipolar resonances by about one order of magnitude, which is consistent with our numerical simulations. These findings open new possibilities for the optimization of upconversion processes on the nanoscale through the appropriate engineering of suitable dielectric materials.

Optically resonant dielectric nanostructures

“…These particles become nearly invisible in the far-field at the wavelength of anapole excitation. At the same time, the electric field energy is maximized inside the particles at the same wavelength; this was recently confirmed by third-harmonic generation experiments (57). Although the anapole in the dielectric nanodisks originates from mere interference, it provides new perspective for investigations into electromagnetic properties of various chargecurrent distributions.…”

Nonradiating sources, dynamic anapole, and Aharonov-Bohm effect

“…Indeed, a number of recent works have already confirmed the key role of anapole excitations in controlling scattering properties of very simple electromagnetic systems, such as nanodisks and nanowires [15][16][17][18][19][20][21][22][23]. Correspondingly, one may want to revisit the analysis of the electromagnetic response of structurally more complex metamaterials, where the dynamic anapoles could underpin, for example, the microscopic mechanisms of electromagnetic transparency [14] and high-Q effects.…”

Bridging the Gap between Dielectric Nanophotonics and the Visible Regime with Effectively Lossless Gallium Phosphide Antennas

“…using volume generated third harmonic emission, 19 we demonstrate here that the model can also be applied to surface e ects, with the magnitude of the SH intensity, yielding a good measure of the electric energy stored at the dielectric surface.…”