Optimization of surface plasmons launching from subwavelength hole arrays: modelling and experiments

The launching of surface plasmons by micro-gratings of subwavelength apertures milled in a thick metal film is important for the development of surface plasmon based circuits. By comparing the near-field optical images of such surface plasmon sources with the results of a Huygens-Fresnel principle based scattering model, we show that the properties of the locally launched SP beams such as divergence or uniformity can be tuned by adjusting the shape of the micro-gratings. This allows us to propose an optimized source array well adapted for providing a narrow, collimated and uniform beam.