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

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 µm. These heterostructures are functionalized with an array of plasmonic antennas featuring crosspolarized 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.

Influence of Plasmon Resonances and Symmetry Effects on Second Harmonic Generation in WS2–Plasmonic Hybrid Metasurfaces

“…Another field of application, where 1L-TMD draws attention, is the field of plasmonics. Its applications use the same wavelength range from the visible up to near-infrared (NIR) while offering additional properties like strong near-field interactions and large scattering cross sections. , The wide range of applications and well-known physics of tunable plasmonic nanostructures provide a great foundation for implementing them in different types of hybrid metasurfaces. − The combination of 1L-TMDs with plasmonics nanostructures can provide strong light–matter interaction while maintaining very small scales for light manipulation and the possibility of using well-known fabrication methods like electron beam lithography for plasmonic metasurfaces. Although the fabrication process of large-area single-crystalline flakes of 1L-TMD is still challenging, recent progress in monolayer fabrication (e.g., mechanical exfoliation, chemical vapor deposition) may lead to large scale applications, − making it easier for transferring 1L-TMDs onto plasmonic metasurfaces.…”