Rotation of two-petal laser beams in the near field of a spiral microaxicon

Using a spiral microaxicon with the topological charge 2 and NA = 0.6 operating at a 532-nm wavelength and fabricated by electron-beam lithography, we experimentally demonstrate the rotation of a two-petal laser beam in the near field (several micrometers away from the axicon surface). The estimated rotation rate is 55 °/mm and linearly dependent on the on-axis distance, with the theoretical rotation rate being 53 °/mm. The experimentally measured rotation rate is found to be linear and coincident with the simulation results only on the on-axis segment from 1.5 to 3 mm. The experimentally measured rotation rate is 66 °/mm on the initial on-axis segment from 0 to 1.5 mm and 34 °/mm on the final segment of the beam path from 3 to 4.5 mm. The experimentally achieved rotation rate is higher than rotation rates of similar two-petal laser beams reported to date.