Three-dimensional chiral microstructures fabricated by structured optical vortices in isotropic material

TL;DR

This paper introduces a novel method to fabricate three-dimensional chiral microstructures in isotropic materials using coaxial interference of vortex and plane laser beams, enabling controlled chirality and complex structures.

Contribution

The authors develop a new technique employing hologram-designed coaxial interference of vortex and plane beams to create 3D chiral microstructures in isotropic polymers.

Findings

Successful fabrication of 3D chiral microstructures in isotropic polymers.

Chirality controlled by the topological charge of vortex beams.

Technique is simple, stable, and applicable to various optical applications.

Abstract

Optical vortices, as a kind of structured beam with helical phase wavefronts and doughnut shape intensity distribution, have been used for fabricating chiral structures in metal and spiral patterns in anisotropic polarization-dependent azobenzene polymer. However, in isotropic polymer, the fabricated microstructures are typically confined to non-chiral cylindrical geometry due to two-dimensional doughnut intensity profile of optical vortices. Here we develop a powerful strategy for realizing chiral microstructures in isotropic material by coaxial interference of a vortex beam and a plane wave, which produces three-dimensional (3D) spiral optical fields. This coaxial interference beams are creatively produced by designing the contrivable holograms consisting of azimuthal phase and equiphase loaded on liquid-crystal spatial light modulator. Then, in isotropic polymer, 3D chiral microstructures are achieved under illumination of the coaxial interference femtosecond laser beams with their chirality controlled by the topological charge. Our further investigation reveals that the spiral lobes and chirality are caused by the interfering patterns and helical phase wavefronts, respectively. This technique is simple, stable, and easy-operation, and offers broad applications in optical tweezers, optical communications and fast metamaterial fabrication.