Coupling of localized surface plasmons to intersubband transitions in CdO/GaAs

We show here that Cd(Zn)O can be deposited on GaAs by MOCVD forming nanoparticles with a hemispherical shape. These nanoparticles maintain the key characteristics from a CdO film: very high plasma frequency and very low losses, hence retaining the strong plasmonic character. As a result of this, when illuminated with infrared light, two localized surface plasmon (LSP) modes are excited at 2.7 and 5.3 microns, and the electric field is heavily amplified in the underlying GaAs substrate. Moreover, their hemispherical geometry allows them to partially change the orientation of the field, creating a component perpendicular to the surface. We prove the coupling between the CdO LSPs and the intersubband transitions from a multiple QW structure, where the absorption is largely enhanced for p-polarized electric fields, and it is observed even under normal incidence conditions.