The vortex coronagraph is one of the most promising coronagraphs for high contrast imaging because of its simplicity, small inner working angle, high throughput, and clear off-axis discovery space. However, as with most coronagraphs, centrally-obscured on-axis telescopes degrade contrast. Based on the remarkable ability of vortex coronagraphs to move light between the interior and exterior of pupils, we propose a method, based on multiple vortices, that, without sacrificing throughput, reduces the residual light leakage to (a/A)^n, with n >=4, and a and A being the radii of the central obscuration and primary mirror, respectively. This method thus enables high contrasts to be reached even with an on-axis telescope.
@article{arxiv.1103.1909,
title = {Improved High Contrast Imaging with On-Axis Telescopes using a Multi-Stage Vortex Coronagraph},
author = {Dimitri Mawet and Eugene Serabyn and J. Kent Wallace and Laurent Pueyo},
journal= {arXiv preprint arXiv:1103.1909},
year = {2015}
}