Nonlinear dielectric epsilon near-zero hybrid nanogap antennas

TL;DR

This paper explores nonlinear dielectric epsilon near-zero effects in hybrid nanogap antennas, demonstrating enhanced harmonic generation through high refractive index contrast and field confinement in ITO-GaP structures.

Contribution

It introduces a novel hybrid nanogap antenna design with ITO and GaP, showing how to boost nonlinear optical signals at nanoscale resonances.

Findings

Enhanced second and third-harmonic signals at resonance

Strong field confinement inside the ITO layer

Insights into nonlinear susceptibilities for device engineering

Abstract

High-index Mie-resonant dielectric nanostructures provide a new framework to manipulate light at the nanoscale. In particular their local field confinement together with their inherently low losses at frequencies below their band-gap energy allows to efficiently boost and control linear and nonlinear optical processes. Here, we investigate nanoantennas composed of a thin indium-tin oxide layer in the center of a dielectric Gallium Phosphide nanodisk. While the linear response is similar to that of a pure GaP nanodisk, we show that the second and third-harmonic signals of the nanogap antenna are boosted at resonance. Linear and nonlinear finite-difference time-domain simulations show that the high refractive index contrast leads to strong field confinement inside the antenna's ITO layer. Measurement of ITO and GaP nonlinear susceptibilities deliver insight on how to engineer nonlinear nanogap antennas for higher efficiencies for future nanoscale devices.