Abstract
Enhancing the second harmonic conversion efficiency at the nanoscale is a critical challenge in nonlinear optics. Here we propose the use of epsilon-near-zero materials to boost the nonlinear radiation in the far field. Here, a comparison of the second harmonic behavior of a cylindrical AlGaAs nanoantenna placed over different semi-infinite layers is presented. In particular, we observed that the second harmonic generation is strongly enhanced and redirected by the simultaneous presence of a resonance at the fundamental wavelength and a low-permittivity condition in the substrate at the harmonic wavelength. Our results pave the way for a novel approach to enhance optical nonlinearities at the nanoscale.
Highlights
Dielectric nanoantennas have recently gained increasing interest for many applications such as directional scattering and emission, nonlinear spectroscopy and microscopy [1,2,3,4]
The conversion efficiencies reported were higher than 10−5 [6,7,8], which is more than four orders of magnitude greater than optimized centrosymmetric plasmonic nanoantennas pumped at similar intensities
At a fundamental wavelength (FW) of 1550 nm with incident amplitude E0 corresponding to a pump intensity of 1.6 GW/cm2
Summary
Dielectric nanoantennas have recently gained increasing interest for many applications such as directional scattering and emission, nonlinear spectroscopy and microscopy [1,2,3,4]. A nanoscale system based on AlGaAs nanodisks placed over an AlOx substrate pumped in the telecom range was theoretically proposed as an efficient system to enhance second-order nonlinear effects in nanoscale optics [5]. We demonstrate how one can exploit the peculiar ability of ENZ substrates to re-direct the electromagnetic radiation to increase the efficiency of nonlinear processes generated in AlGaAs nanoantennas.
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