  We report a quantitative analysis of the wavevector diagram emitted by
nonlinear photoluminescence generated by a tightly focused pulsed laser beam
and distributed along Au nanowire via the mediation of surface plasmon
polaritions. The nonlinear photoluminescence is locally excited at key
locations along the nanowire in order to understand the different contributions
constituting the emission pattern measured in a conjugate Fourier plane of the
microscope. Polarization-resolved measurements reveal that the nanowire
preferentially emits nonlinear photoluminescence polarized transverse to the
long axis at close to the detection limit wavevectors with a small azimuthal
spread in comparison to the signal polarized along the long axis. We utilize
finite element method to simulate the observed directional scattering by using
localized incoherent sources placed on the nanowire. Simulation results
faithfully mimic the directional emission of the nonlinear signal emitted by
the different portions of the nanowire.
