Vectorial Helico-Conical beams

TL;DR

This paper introduces a new family of vector beams called Helico-Conical Vector Beams (HCVB), demonstrating their unique polarization evolution and potential applications in optical manipulation and secure communication.

Contribution

The work presents the experimental creation and analysis of HCVBs, revealing their polarization dynamics and introducing the Hellinger distance as a novel metric for vectorness.

Findings

Polarization distribution evolves from non-homogeneous to quasi-homogeneous during propagation.

Global degree of nonseparability remains constant, local degree decreases to a minimum.

HCVBs are only the second family exhibiting this behavior, enabling new applications.

Abstract

In this work, we propose and demonstrate experimentally a new family of vector beams, the Helico-Conical Vector Beams (HCVB), whose spatial degree of freedom is encoded in the Helico-Conical Optical Beams. We use Stokes polarimetry to study their properties and find that upon propagation their transverse polarisation distribution evolves from non-homogeneous to quasi-homogeneous, such that even though their global degree of nonseparability remains constant, locally it decreases to a minimum value as z tends to infinit. We corroborated this quantitatively using the Hellinger distance, a novel metric for vectorness that applies to spatially-disjoint vector modes. To the best of our knowledge, HCVBs are the second family of vector beams in which this behaviour has been observed, paving the way for applications in optical tweezing or information encryption.