Longitudinal field controls vector vortex beams in anisotropic epsilon-near-zero metamaterials

TL;DR

This paper introduces a novel method for controlling vector vortex beams with longitudinal components using anisotropic epsilon-near-zero metamaterials, enabling advanced wavefront and polarization engineering for optical applications.

Contribution

It demonstrates how anisotropic epsilon-near-zero metamaterials can manipulate complex vector beams, revealing new control mechanisms for their polarization and modal content.

Findings

Propagation of complex beams is strongly affected by metamaterial anisotropy.

Longitudinal fields interact uniquely with epsilon-near-zero metamaterials.

Control of polarization singularities enables beam filtering and shaping.

Abstract

Structured light plays an important role in metrology, optical trapping and manipulation, communications, quantum technologies, nonlinear optics and provides a rich playground for addressing new optical phenomena. Here we demonstrate a novel approach for manipulating vector vortex beams carrying longitudinal field components using metamaterials with extreme anisotropy. Implementing vectorial spectroscopy, we show that the propagation of complex beams with inhomogeneous polarisation is strongly affected by the interplay of the metamaterial anisotropy with the transverse and longitudinal field structure of the beam. This phenomenon is especially pronounced in the epsilon-near-zero regime, exclusively realised for light polarised along the metamaterial optical axis, strongly influencing the interaction of longitudinal fields with the metamaterial. The requirements on the balance between the transverse and longitudinal fields to maintain a polarisation singularity at the beam axis allow control of the beam modal content, filtering diffraction effects and tailoring spatial polarisation distribution. The proposed approach offers important capabilities for wavefront shaping as well as local spatial polarisation engineering. The understanding of the interaction of vector beams with metamaterials opens new opportunities for applications in microscopy, information encoding, biochemical sensing and quantum technologies.