External seminar | 05 September 2025

Optical vortices are fascinating objects with deep connection to waves of any nature. When multiple waves interfere destructively, isolated points of darkness appear. Because the amplitude is zero, phase is undetermined, or singular, and it forms a screw-type dislocation around the dark spot. 

Energy flow follows the twisted phase, hence the name "vortex''. In three-dimensional space the field nodal lines, or "threads of darkness'', need not be straight, as in Laguerre-Gaussian laser beams. Vortex lines can bend and loop into vortex rings. The rings can deform and reconnect, and I will demonstrate a rich variety of topological transformations of optical vortex rings. The rings need not be simply connected, they can be linked and knotted, and I will discuss how the nonlinear waves can form vortex rings and vortex knots spontaneously.