18 July 2014 A broadband scalar optical vortex coronagraph
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In recent years, new coronagraphic schemes have been proposed, the most promising being the optical vortex phase mask coronagraphs. In our work, a new scheme of broadband optical scalar vortex coronagraph is proposed and characterized experimentally in the laboratory. Our setup employs a pair of computer generated phase gratings (one of them containing a singularity) to control the chromatic dispersion of phase plates and achieves a constant peak-to-peak attenuation below 1:1000 over a bandwidth of 120 nm centered at 700 nm. An inner working angle of λ/D is demonstrated along with a raw contrast of 11.5magnitudes at 2λ/D. A more compact setup achieves a peak-to-peak attenuation below 1:1000 over a bandwidth of 60 nm with the other results remaining the same.
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Ronnie Errmann, Ronnie Errmann, Stefano Minardi, Stefano Minardi, Thomas Pertsch, Thomas Pertsch, } "A broadband scalar optical vortex coronagraph", Proc. SPIE 9151, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation, 91515M (18 July 2014); doi: 10.1117/12.2054875; https://doi.org/10.1117/12.2054875

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