  We investigate the enhanced electric dipole-dipole interaction by surface
plasmon polaritons (SPPs) supported by the planar metal film waveguide. By
taking two nitrogen-vacancy (NV) center electric-dipoles in diamond as an
example, both the coupling strength and collective relaxation of two dipoles
are studied with numerical Green Function method. Compared to the two-dipole
coupling on planar surface, metal film provides stronger and tunable coupling
coefficients. Enhancement of the interaction between coupled NV center dipoles
could have applications in both quantum information and energy transfer
investigation. Our investigation provides a systematical result for
experimental applications based on dipole-dipole interaction mediated with SPPs
on planar metal film.
