Abstract
A concept of new SNOM probe is based on a reversal structure of so-called "bow tie" probe. The apex of the probe is masked by metal thin film, and the aperture consists of a square hole, 100 nm on a side, and the adjacent square hole of the same shape. The computer simulation based on the boundaly element method has suggested that the above structure on a silver thin film forms an intense focusing point of surface plasmons at the end of the confining wall. We have started to validate the evidence of the focusing point experimentally. The two hole structure described above is made on thin films of silver and aluminum. The two holes are back-lighted by a He-Ne laser. A 500 nm gold protrusion is used as a probe to scan over the holes. In the resultant scan image composed of an intensity of scattered light from the protrusion, a blurred luminescent spot has been observed around the two holes in a reproducible fashion. But such the luminescent spot has not been observed by the SNOM system with a 500 nm polystylene sphere as the probe. The reason might be caused of an optical interference between two laser beams, one illuminates the probe and the other back-lights the holes.
