On a method for obtaining laser beams with a phase singularity

A method is analysed for obtaining laser beams with a phase singularity with the help of phase screens described by the function of the type exp(ilφ). It is shown that this method is used to obtain laser beams in the form of single rings with a smooth intensity distribution in the far-field radiation zone (at the lens focus) representing the superposition of Laguerre–Gaussian modes. In the near-field zone and, in the presence of aperture clipping, also in the focal region, the beams with a more complicated structure can be observed. The scaling of the radius corresponding to the maximum intensity of the beam both in the absence and presence of aperture clipping occurs linearly with the singularity charge l. The influence of the beam decentration and of the phase screen on the structure of phase-singularity beams is estimated.