Optical vortices with starlight: Implications for ground-based stellar coronagraphy

TL;DR

This study demonstrates the use of optical vortices generated from starlight for ground-based stellar coronagraphy, showing promising results under poor seeing conditions and opening new avenues for astronomical observations.

Contribution

It introduces a method to produce and analyze optical vortices from starlight using a blazed fork-hologram and applies vortex coronagraphy to ground-based telescopes, aligning with theoretical predictions.

Findings

Optical vortices were successfully generated from stellar light.

Vortex coronagraphy effectively suppressed starlight in observations.

Results agree with theoretical models and simulations.

Abstract

Using an l = 1 blazed fork-hologram at the focal plane of the Asiago 122 cm telescope, we obtained optical vortices from the stellar system Rasalgethi (alpha Herculis) and from the single star Arcturus (alpha Bootis). We have analyzed the structure of the optical vortices obtained from non-monochromatic starlight under very poor seeing conditions using a fast CCD camera to obtain speckle patterns and carry out the lucky imaging technique, alternative to adaptive optics. With the insertion of a red filter and of a Lyot stop we performed l = 1 optical vortex coronography the double star HD74010. The results are in agreement with theory and numerical simulations. Our results open the way to applications of optical vortices to ground based astronomical observations, in particular for coronagraphy with l > 1 masks. No intrinsic orbital angular momentum was detected in the starlight.