  Microcavity polaritons are bosonic light-matter particles that can emit
coherent radiation without electronic population inversion via bosonic
scattering. This phenomenon, known as polariton lasing, strongly depends on the
polaritons' confinement. Shrinking the polaritons' mode volume increases the
interactions mediated by their excitonic part, and thereby the
density-dependent blueshift of the polariton to a higher energy is enhanced.
Previously, polariton lasing has been demonstrated in micropillars with
diameters larger than three microns, in grating based cavities, fiber cavities
and photonic crystal cavities. Here we show polariton lasing in a micropillar
with one micron diameter operating in a single transverse mode that can be
optimally coupled to a singlemode fiber. We geometrically decouple the
excitation with an angle from the collection. From the number of collected
photons we calculate the number of polaritons and observe a blueshift large
enough to qualify our device for novel schemes of quantum light generation such
as the unconventional photon blockade. To that end, we also apply angled
excitation to polaritonic molecules and show site-selective excitation and
collection of modes with various symmetries.
