Belarusian State University, Беларусь

Research of optical vortices and their applications is a promising area of modern photonics. A key characteristic of an optical vortex is its topological charge, which is characterized by the degree and direction of wavefront twist. Using topological charge, which is conserved during light beam propagation, enables efficient information encoding. This provides an additional information parameter that, along with polarization, amplitude, and wavelength, can contribute to optical information transmission. This paper proposes an interference method for diagnosing the phase topology of singular light beams (optical vortices), offering an alternative to existing interference and diffraction methods. A technique for determining the topological charge of an optical vortex has been developed using a holographic asymmetric lens recorded in a photorefractive bismuth silicate crystal. An off-axis holographic recording scheme for transmission holograms was employed. At the focus of the recorded lens, the optical vortex disintegrates into vortices with a single charge. The singularity regions of these vortices are aligned as spots, the number of which allows one to determine the magnitude of the topological charge. The sign of the topological charge is determined by the direction of the line tilt in the focal plane. An advantage of using photorefractive crystals to record holographic elements is the ability to repeatedly record and use the same holographic optical element to implement various functional operations.