Generation and propagation of an open vortex beam

TL;DR

This paper introduces open vortex beams (OVBs), a new class of vortex beams with open ring structures and controllable topological charge, generated via diffraction by partially blocked fork-shaped gratings, with both theoretical modeling and experimental validation.

Contribution

The paper presents the first theoretical and experimental study of OVBs, including their generation, propagation characteristics, and potential applications, expanding the understanding of vortex beam structures.

Findings

OVBs can have both open ring structures and integer topological charges.

Propagation causes a $rac{ ext{pi}}{2}$ rotation of the open ring due to Gouy phase shift.

Experimental results agree well with theoretical models.

Abstract

We theoretically and experimentally studied a novel class of vortex beams named open vortex beams (OVBs). Such beams are generated using Gaussian beams diffracted by partially blocked fork-shaped gratings (PB-FSGs).The analytical model of OVBs in the near field and far field is given by superpositions of Hypergeometric (HyG) modes. Unlike conventional integer and fractional vortex beams, the OVBs can have both an open ring structure and an integer topological charge (TC). The TC is decided by the circumference covered by the open ring. It is also quantitatively shown that a $\pi/2$ rotation of the open ring occurs in the propagation of an OVB due to the Gouy phase shift. Futhermore, we demonstrate experimental generation and detection of OVBs. Our experimental results are in very good agreement with the theory. We believe that the OVB can be the potential candidate for numerous applications, such as particle manipulation, quantum information and optical metrology.