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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