Bragg-Berry mirrors: reflective broadband q-plates

TL;DR

This paper demonstrates flat, broadband mirrors that generate optical vortices through the geometric Berry phase in chiral liquid crystal films, enabling robust spin-orbit photonic devices across the visible spectrum.

Contribution

It introduces a novel broadband reflective q-plate design based on Berry phase, not requiring birefringent retardation, for efficient optical vortex generation.

Findings

Broadband optical vortex generation over the full visible spectrum.

Reflective spin-orbit phase manipulation without birefringent retardation.

Successful demonstration with both diffractive and nondiffractive beams.

Abstract

We report on the experimental realization of flat mirrors enabling the broadband generation of optical vortices upon reflection. The effect is based on the geometric Berry phase associated with the circular Bragg reflection phenomenon from chiral uniaxial media. We show the reflective optical vortex generation from both diffractive and nondiffractive paraxial light beams using spatially patterned chiral liquid crystal films. The intrinsic spectrally broadband character of spin-orbit generation of optical phase singularities is demonstrated over the full visible domain. Our results do not rely on any birefringent retardation requirement and consequently foster the development of a novel generation of robust optical elements for spin-orbit photonic technologies.