Near-Field Diffraction from a Binary Microaxicon

Abstract EN

We study binary axicons of period 4, 6, and 8 μm fabricated by photolithography with a 1 μm resolution, 500 nm depth, and 4 mm diameter.

Near-field diffraction focal spots varying in diameter from 3.5λ to 4.5λ (for the axicon of period T=4 μm) and from 5λ to 8λ (for the axicon with T=8 μm) are experimentally found on the optical axis at a distance of up to 40 μm from the axicon for the wavelength λ=0.532 μm.

The first focal spot is found at distance 2 μm (T=4 μm), with the period of the focal spots being 2 μm (T=4 μm) and 4 μm (T=8 μm).

Diffraction of linearly polarized plane and diverging waves is simulated using FullWAVE (RSoft) and a proprietary program BOR-FDTD, which implement finite-difference schemes to solve three-dimensional Maxwell's equations in the Cartesian and cylindrical coordinates.

The numerically simulated values for diameters of the near-field focal spots for the axicon of period T=4 μm are in good agreement with the experimental values.