Authors

Alexis Carlotti (1), Laurent Pueyo (2)

Affiliations

(1) Princeton University; (2) JPL

Abstract

It has been shown that the PIAA coronagraph cannot achieve on its own the theoretical performances derived from the ray optics approximation. Additional pre and post-apodizers can however weaken the diffraction effects between the two optical elements (in our case two mirrors) and provide contrasts and throughputs closer those initially expected. For a given apodization strength, set by the prolateness parameter that defines the apodizer, and considering the physical limitations of the mirrors (their diameters, maximum height, curvature, and the distance between them), one can derive the properties of the pre and post-apodizers which make it possible to achieve a desired contrast at a certain distance from the star, possibly at the price of a lower throughput. In the visible and in the J, H and K bands we consider several pairs of mirrors and propose in each cases possible choices of pre and post-apodizers. The possibility of using two deformable mirrors is particularly discussed. We also present binary versions of the post-apodizers that we find through a broadband optimization of the PSF.