Generation of fractional optical vortices at the edge of the phase wedge

We have made a theoretical modeling of the evolution of a monochromatic Gaussian beam diffracted by the angle formed by three sides of the phase wedge different types. We have found that the edges of the phase wedge generate macroscopic chains of identical optical vortices that disappear at the far field zone. At the same time, the π -phase plate can reproduce a very complex wave field whose structure depends on the scale of observation. At large scales there appear two π -cuts resembling broken edge dislocations with perpendicular directions. At small (some microns) scales two short vortex chains consisting of alternating-sign optical vortices are nucleated near the corner of the wedge. The analysis shows that the sizes of the chains decrease quickly when approaching the wedge surface. This enables us to assume that the π -phase plate can create so-called optical quarks in the evanescent waves of the edge field. On the basis of theoretical considerations experiment was conducted in which were obtained fractions optical vortices at the edge of the phase wedge.