  Coupling of higher-order-mode light into a single sliver nanowire and the
degree of the coupling can be controlled by adjusting the light polarization,
showing that nanowire waveguide has no request on the spatial mode of the input
light. Photons with different orbital angular momentums (OAM) are used to
excite surface plasmons of silver nanowires. The experiment indicates the
propagating modes of surface plasmons in nanowires were not the OAM
eignenstates.
