Tight focusing with a binary microaxicon

Abstract

Using a near-field scanning microscope (NT-MDT) with a 100nm aperture cantilever held 1 μm apart from a microaxicon of diameter 14 μm and period 800nm, we measure a focal spot resulting from the illumination by a linearly polarized laser light of wavelength λ ¼ 532nm, with itsFWHMbeing equal to 0:58λ, and the depth of focus being 5:6λ. The rms deviation of the focal spot intensity from the calculated value is 6%. The focus intensity is five times larger than the maximal illumination beam intensity.