K. Regelskis

Propagation of Bessel beams carrying optical vortices

The variation of the vorticity of the superposition of two Bessel singular beams under free-space propagation is analyzed. We demonstrate that in the near field the combined beam creates light pattern with much richer vortex content than that of individual beams. Under diffraction the combined beam dynamically evolves into the beam with rather simple vortical structure in the far field. A qualitative agreement of experimental results with theoretical predictions is obtained.

Nonlinear self-reconstruction of truncated Bessel beam

It is demonstrated that by blocking of the part of Bessel light beam azimuthal aperture, a far field ring is completely reconstructed in azimuth and partially in intensity after the beam passes through a benzene cell. The phenomenon is explained as beam self-action (degenerate four-wave mixing) in the medium with Kerr nonlinearity. A qualitative agreement of the theoretical predictions with experimental results is obtained.

Noncollinear interaction of optical vortices in Kerr nonlinear medium

The noncollinear interaction of singular light beams (degenerate four-wave mixing) in Kerr nonlinear medium is analyzed. It is demonstrated that vorticity of diffracted beams significantly depends on the topological charges of pump beams. The results of an experimental observation of the phenomenon are presented.

Free-space propagation of second harmonic Laguerre-Gaussian beams carrying phase singularity

The vorticity of a free propagating second harmonic (SH) beam produced in a nonlinear quadratic crystal by a combined beam composed of two coaxial Laguerre–Gaussian vortex beams is analysed. In the near field of the SH radiation an aligned vortical structure with a number of double-charge vortices is created. The diffraction of the SH beam under free propagation is also discussed.

Free-space propagation of second harmonic beams carrying optical vortices

Abstract A vorticity of free propagating SH beam produced in nonlinear crystal by combined beam composed of two coaxial Laguerre–Gaussian vortex beams is analyzed. It is revealed that the vortical structures of SH beam in the near and far fields are different when two vortex beams are carrying vortices with topological charges of different signs. The diffraction of SH beam under free propagation is investigated. A qualitative agreement of the theoretical predictions with experimental results is obtained.

Parametric down-conversion of higher-order Bessel beams in nonlinear crystals

It is revealed that orbital angular momentum can be conserved within the spontaneous parametric down-conversion of higher-order Bessel beam. A qualitative agreement of theoretical predictions with experimental results is obtained.

Parametric down-conversion of Bessel vortex beam in quadratic medium

This study predicts and demonstrates that orbital angular momentum (OAM) is conserved within the spontaneous down-conversion of Bessel vortex beam in optical parametric generators (OPG). Results show that the output radiation of CDA-based OPG pumped by Bessel vortex beam consists of two pairs of OAM-free axial (Gaussian-like) beam and the conical (Bessel-like) beam, the OAM of which is equal to OAM of pump beam. Hence, the OAM is conserved within the spontaneous parametric down-conversion of higher-order Bessel beams in contrary to OPG pumped by Laguerre-Gaussian modes. That is the result of strong transverse selection of spontaneously arising fields in OPG pumped by Bessel beams.