Requirements on optical density and phase dispersion of imperfect band-limited occulting masks in a broadband coronagraph

• Published in: Applied optics (2004) 2007-10, Vol.46 (30), p.7485-7493
• Main Author: Sidick, Erkin
• Format: Article
• Language: English
• ISSN: 1559-128X
• DOI: 10.1364/AO.46.007485

We investigate the effects of the parasitic phase of imperfect band-limited occulting masks on the broadband contrast performance of a high-contrast imaging system through modeling and simulations. We also examine the effects of the phase and the optical-density dispersions of occulting masks whose parasitic phase has been compensated at the center wavelength but is nonzero at other wavelengths. Two types of occulting masks are considered: gray-scale masks such as those made on a high-energy beam-sensitive glass, and recently proposed spatially profiled metal masks, both having 1D Sinc2(linear-Sinc2) amplitude transmission coefficient (Sinc4 intensity transmittance) profiles. We determine the conditions for obtaining 1x10(-9) and 1x10(-10) contrast values with a light centered at a 785 nm wavelength and having a 10% bandwidth in a coronagraphic telescope having ideal optical surfaces but imperfect band-limited image-plane occulting masks.