  The research area of plasmonics promises devices with ultrasmall footprint
operating at ultrafast speeds and with lower energy consumption compared to
conventional electronics. These devices will operate with light and bridge the
gap between microscale dielectric photonic systems and nanoscale electronics.
Recent research advancements in nanotechnology and optics have led to the
creation of a plethora of new plasmonic designs. Among the most promising are
nanoscale antennas operating at optical frequencies, called nanoantennas.
Plasmonic nanoantennas can provide enhanced and controllable light-matter
interactions and strong coupling between far-field radiation and localized
sources at the nanoscale. After a brief introduction of several plasmonic
nanoantenna designs and their well-established radio-frequency antenna
counterparts, we review several linear and nonlinear applications of different
nanoantenna configurations. In particular, the possibility to tune the
scattering response of linear nanoantennas and create robust optical wireless
links is presented. In addition, the nonlinear and photodynamic responses of
different linear and nonlinear nanoantenna systems are reported. Several future
optical devices are envisioned based on these plasmonic nanoantenna
configurations, such as low-power nanoswitches, compact ultrafast light
sources, nanosensors and efficient energy harvesting systems.
