  Exciton-polaritons in semiconductor microcavities have advanced to become a
model system for studying dynamical Bose-Einstein condensation, macroscopic
coherence, many-body effects, nonclassical states of light and matter, and
possibly quantum phase transitions in a solid state. Being low mass bosons,
these light-matter quasiparticles can condense at comparably high temperatures
up to 300K, while preserving fundamental properties such as coherence in space
and time domain even when they are out of equilibrium with the environment.
Although the presence of an in-plane polariton confinement potential is not
strictly necessary in order to observe condensation of polaritons, engineering
the polariton confinement is a key to controlling, shaping and directing the
flow of polaritons. Prototype polariton-based optoelectronic devices rely on
ultrafast photon-like velocities and strong nonlinearities, as well as on
tailored confinement. Nanotechnology provides several pathways to achieving
such a confinement, and the specific features and advantages of the different
techniques are discussed in this paper. As hybrid exciton-photon
quasiparticles, polaritons can be trapped via their excitonic as well as their
photonic component, which leads to a wide choice of highly complementary
techniques. Here we highlight the almost free choice of trapping geometries and
depths of confinement that provides a powerful tool for control and
manipulation of polariton systems both in semi-classical and quantum domain.
Furthermore, the possibility to observe effects of polariton blockade, Mott
insulator physics, and population of higher-order bands in sophisticated
lattice potentials is discussed. The observation of such effects will signify
the opportunity for the realization of novel polaritonic non-classical light
sources and quantum simulators.
