Subwavelength focusing using a binary microaxicon with period 800 nm

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 mkm, 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 mkm 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 0.54(lambda). The peak intensity on the optical axis is 7 times higher than the illuminating beam intensity.