Analysis of the light transmission through nano-apertures on plateau pyramid

Abstract

The nano-size metallic aperture array has been fabricated using conventional semiconductor fabrication techniques and focused ion beam. The micron size patterns were transferred on SOI wafer using photographic patterning process, and the plateau pyramidal structures were fabricated using wet Si etching with alkaline solution followed by thermal oxidation. In order to reveal the plateau type pyramid, the backside Si bulk etching was performed. The metallic Al thin film was deposited and the nano-apertures with the diameters ranging from 190 nm to 380 nm were fabricated using focused ion beam milling method. The skin-depth of the Al thin film at 532 nm wavelength is known to be ∼10 nm. The deposited Al thin film is thick enough to become opaque. Circular types of periodic grooves were fabricated around the sub-wavelength size nano-aperture in order to examine the transmittance of the light coupled to circular periodic grooves. The far-field measurements for the optical transmittance through a sub-wavelength size nano-probe have been investigated and found to be up to 10 3 fold increase, compared to the output intensity of aperture without groove patterns.