  We experimentally demonstrate that a linear dipole is not restricted to emit
linearly polarised light, provided it is embedded in the appropriate
nanophotonic environment. We observe emission of various elliptical
polarisations by a linear dipole including circularly polarised light, without
the need for birefringent components. We further show that the emitted state of
polarisation can theoretically span the entire Poincare sphere. The
experimental demonstration is based on elongated gold nanoparticles (nanorods)
deposited on an optical nanofibre and excited by a free-space laser beam. The
light directly collected in the guided mode of the nanofibre is analysed in
regard to the azimuthal position and orientation of the nanorods, observed by
means of scanning electron microscopy. This work constitutes a demonstration of
the mapping between purely geometrical degrees of freedom of a light source and
all polarisation states and could open the way to new methods for polarisation
control of light sources at the nanoscale.
