Narrow high refractive index nanowires
sustain weakly guided modes with significant mode volume outside of
the nanowire. This modal spillover makes them interesting photonic
materials for a multitude of applications. In this article we fabricate
dimers of nanowires with lengths up to 1.4 μm, radii down to
55 nm, and edge-to-edge separation down to 60 nm through anisotropic
etching from crystalline silicon (Si). We investigate how the properties
of the weakly confined fundamental HE1,1 mode in Si nanowires
are modified by their integration into dimers. In particular, we characterize
through a combination of experimental spectroscopy and numerical electromagnetic
simulations how the lifting of the degeneracy of HE1,1x
and HE1,1y
modes in
dimers of Si nanowires generates linear birefringence, spin angular
momentum, and superchirality. Achiral Si nanowire dimers are found
to create locations of strongly enhanced near-field chirality in the
gap between the nanowires, where the field can interact with the ambient
medium.