  We report on the experimental observation of mirror enhanced directional
surface enhanced Raman scattering (SERS) from a self-assembled monolayer of
molecules coupled to a nanowire-nanoparticle (NW-NP) junction on a mirror in
remote excitation configuration. Placing NW-NP junction on a metallic mirror
generates multiple gap plasmon modes which have unique momentum space
scattering signatures. We perform Fourier plane imaging of SERS from NW-NP on a
mirror to understand the effect of multiple hotspots on molecular emission. We
systematically study the effect of ground plane on the directionality of
emission from NW-NP junction and show that the presence of a mirror drastically
reduces angular spread of emission. The effect of multiple hotspots in the
geometry on directionality of molecular emission is studied using 3D numerical
simulations. The results presented here will have implications in understanding
plasmon hybridization in the momentum space and its effects on molecular
emission.
