We theoretically characterize the collective radiative behaviour of N classical emitters near an interface between different dielectrics that supports the transfer of surface plasmon modes into the far-field of electromagnetic radiation. The phenomen
a of superradiance and surface plasmons can be combined to amplify the emitted radiation intensity S as S= A N^2 S_0 compared to a single emitters intensity S_0 in free space. For a practical case study within the paper A=240, compared to A=1 in free space. We furthermore demonstrate that there are collective modes for which the intensity of the emitted radiation is suppressed by two orders of magnitude despite their supperadiant emission characteristics. A method to control the emission characteristics of the system and to switch from super- to sub-radiant behaviour with a suitably detuned external driving field is devised.
