A nonlinear metasurface combining telecom-range intersubband transitions in GaN/AlN quantum wells with resonant plasmonic antenna arrays

TL;DR

This paper demonstrates a nonlinear metasurface using GaN/AlN quantum wells and plasmonic antennas to achieve efficient second-harmonic generation at telecom wavelengths, with controllable emission directions.

Contribution

It introduces a novel nonlinear metasurface combining quantum well heterostructures with plasmonic antennas for enhanced second-harmonic generation in the telecom range.

Findings

Substantial second-harmonic generation observed at normal incidence.

Directional control of second-harmonic emission achieved.

Enhanced nonlinear response due to quantum well and antenna integration.

Abstract

We realize and investigate a nonlinear metasurface taking advantage of intersubband transitions in ultranarrow GaN/AlN multi-quantum well heterostructures. Owing to huge band offsets, the structures offer resonant transitions in the telecom window around 1.55 $\mu$m. These heterostructures are functionalized with an array of plasmonic antennas featuring cross-polarized resonances at these near-infrared wavelengths and their second harmonic. This kind of nonlinear metasurface allows for substantial second-harmonic generation at normal incidence which is completely absent for an antenna array without the multi-quantum well structure underneath. While the second harmonic is originally radiated only into the plane of the quantum wells, a proper geometrical arrangement of the plasmonic elements permits to redirect the second-harmonic light to free-space radiation, which is emitted perpendicular to the surface.