Concentric Nano Elliptical Apertures Array Tip for Intensity Enhancement
in Scanning Near-Field Optical Microscopy for Imaging
Abstract
One of the advantages of light controlling is the enhancement of its
intensity in localization of the beam in the near- and far-fields. Our
desire is to design a concentric nano elliptical apertures array tip
(CNEAAT) for this purpose. The array tip manipulates the incident light
by the nano elliptical apertures with sizes smaller than half-wavelength
of the incident photons over the visible spectral range. The designed
array tip generates the beam with the improved optical characteristics
for maximum intensity enhancement at a special direction of far-field
points. The light is steered to examine the output beam of the CNEAAT at
various elevation angles in the near-field. For a special scanned
impinged angle, the CNEAAT irradiation is focused on an assigned
material under-test (MUT) for study of the beam enhancement. The MUT is
inserted inside a cylindrical reservoir. The reservoir is inscribed by
wall with n=1 and height of 40μm, includes the cross-section radius of
138nm and a metal bottom. In our design, the MUT is assumed to have real
permittivity, as a sample to test the intensity enhancement of the
impinged and transmission beams. The intensity enhancement obtained by
the CNEAAT is anticipated comparable with the standardized apertures
arrays. The design is found to be used in the numerous applications
analogous to scanning near-field optical microscopy (SNOM) for imaging.