Focusing of light by a nanohole array

We demonstrate a conceptually new mechanism for focusing at optical frequencies based upon the use of nano-hole quasi-periodic arrays in metal screens. Using coherent illumination at 660nm and scanning near-field optical microscopy, ~ 290nm "hot spots", were observed at a distance of ~ 12:5µm from the array. Even smaller hot-spots of about 200nm in waist were observed closer to the plane of the array.