Subwavelength focusing using a binary microaxicon with period 800 nm
V.V. Kotlyar, S.S. Stafeev, M.I. Shanina, A.A. Morozov, V.A. Soifer, L. O'Faolain

Image Processing Systems Institute, Russian Academy of Sciences,

Samara State Aerospace University,

School of Physics and Astronomy, University of St. Andrews, Scotland

Full text of article: Russian language.

Abstract:
Using a scanning near-field optical microscope NT-MDT and a cantilever with aperture size 100 nm positioned 100 nm above the surface of a microaxicon of diameter 13.6 μm, period 800 nm and depth 465 nm (manufactured jointly by the IPSI RAS and the University of the St. Andrews (Scotland) using the e-beam lithography on ZEP520A resist) we obtained a focal spot whose diameter at full-width half maximum (FWHM) is 0.61 of the incident wavelength. The depth of focus at FWHM equals 3 μm and the experimental values of the axial intensity on the focal line are in good agreement with the calculated values of the axial intensity (RMS equals 13%). The theoretical value of the focal spot size at FWHM equals 0.54λ. The peak intensity on the optical axis is 7 times higher than the illuminating beam intensity.

Key words:
binary microaxicon, near-field scanning optical microscopy, FDTD-method, laser beam subwavelength focusing.

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