Subdiffraction light focusing on a grating substrate.
We describe a way to generate subdiffraction light spots that can be moved over a surface without resorting to near-field manipulation, nonlinear effects, or negative index materials. We use a periodically patterned substrate that converted efficiently, through scattering, the impinging propagative waves into evanescent ones. Then we optimize the wave front of the incident propagative beam so that the grating-scattered evanescent waves interfere constructively at the focal point. Numerical simulations show that focus spots as small as one-sixth of a wavelength can be obtained at any point on the substrate. One foreseen application is high resolution surface imaging.
Sentenac
Anne
A
Institut Fresnel (UMR 6133), Université d'Aix-Marseille III, Avenue Escadrille Normandie-Niemen, F-13397 Marseille cedex 20, France. anne.sentenac@fresnel.fr
Chaumet
Patrick C
PC