Arrays of optical vortices formed by "fork" holograms

TL;DR

This paper investigates the entire set of optical vortex beams generated by fork holograms, revealing interference patterns that confirm the Kummer beam model and allow phase singularity characterization.

Contribution

It extends the study from single beams to the full set of diffracted OV beams, demonstrating their mutual interference and pattern formation under certain conditions.

Findings

Interference patterns reveal the spatial properties of diffracted OV beams.

Patterns confirm the Kummer beam model for diffracted beams.

Method to determine phase singularity sign and magnitude.

Abstract

Singular light beams with optical vortices (OV) are often generated by means of thin binary gratings with groove bifurcation ("fork holograms") that produce a set of diffracted beams with different OV charges. Usually, only single separate beams are used and investigated; here we consider the whole set of diffracted OV beams that, at certain conditions, are involved in efficient mutual interference to form a characteristic pattern where the ring-like structure of separate OV beams is replaced by series of bright and dark lines between adjacent diffraction orders. This pattern, well developed for high diffraction orders, reflects the main spatial properties of the diffracted beams as well as of the fork grating used for their generation. In particular, it confirms the theoretical model for the diffracted beams (Kummer beam model) and enables to determine the sign and the absolute value of the phase singularity embedded in the hologram.