Period of “droplet” quasi-Bessel beam generated with the round-tip axicon

We demonstrate the experimental study of the axial intensity distribution of a quasi-Bessel beam with a droplet structure of the central core, formed by an axicon with the round-tip, and the results of the theoretical calculations. We show that the period of “droplet” quasi-Bessel beam is determined by the shape of the surface rounding and the angle at the top of the axicon lens and depends on the distance to it. The analysis of this dependence makes it possible to restore the shape of the round-tip of the axicon without 3D scanning.