Optical Vectorial Vortex Coronagraphs using Liquid Crystal Polymers: theory, manufacturing and laboratory demonstration

TL;DR

This paper presents the development and laboratory testing of an optical vectorial vortex coronagraph using Liquid Crystal Polymers, demonstrating promising results for high-performance, achromatic coronagraphs in astronomical imaging.

Contribution

It introduces a novel method using Liquid Crystal Polymers to generate vectorial vortices for coronagraphy, enabling efficient, achromatic, and low-sensitivity high-contrast imaging.

Findings

Maximum peak-to-peak attenuation of 1.4e-2 at 1.55 microns

Residual light level of 3e-5 at 3.5 l/d angular separation

Successful laboratory demonstration of the first prototype device

Abstract

In this paper, after briefly reviewing the theory of vectorial vortices, we describe our technological approach to generating the necessary phase helix, and report results obtained with the first optical vectorial vortex coronagraph (OVVC) in the laboratory. To implement the geometrical phase ramp, we make use of Liquid Crystal Polymers (LCP), which we believe to be the most efficient technological path to quickly synthesize optical vectorial vortices of virtually any topological charge. With the first prototype device of topological charge 2, a maximum peak-to-peak attenuation of 1.4e-2 and a residual light level of 3e-5 at an angular separation of 3.5 l/d (at which point our current noise floor is reached) have been obtained at a wavelength of 1.55 microns. These results demonstrate the validity of using space-variant birefringence distributions to generate a new family of coronagraphs usable in natural unpolarized light, opening a path to high performance coronagraphs that are achromatic and have low-sensitivity to low-order wavefront aberrations.