  We propose and realize a tunable plasmonic nanoantenna design consisting of
two stacked Ag cuboids that are integrated into a rolled-up semiconductor
microtube. The antenna's resonance is tuned by varying the cuboid's distance to
match the photoluminescence emission of an embedded GaAs quantum well.
Spatially, spectrally and temporally resolved photoluminescence measurements
reveal a redshift and a reduction in lifetime of the quantum-well emission as
signatures for the coupling to the antenna system. By means of finite-element
electromagnetic simulations, we assign the coupling to an excitation of a
high-order plasmonic mode inside the Ag cuboids.
