Apodized-pupil Lyot coronagraphs: multistage designs for extremely large telescopes

Abstract

<i>Context. <i/>Earlier apodized-pupil Lyot coronagraphs (APLC) have been studied and developed to enable high-contrast imaging for exoplanet detection and characterization with present-day ground-based telescopes. With the current interest in the development of the next generation of telescopes, the future extremely large telescopes (ELTs), alternative APLC designs involving multistage configuration appear attractive.<i>Aims. <i/>I study the relevance of these designs for the ELTs. My analysis is designed to find out the implications of inherent error sources occurring on large coronagraphic telescopes to the performance of multistage APLC configurations.<i>Methods. <i/>Performance and sensitivity of multistage APLC to ELT specificities are analyzed and discussed, taking into account several ineluctable coronagraphic telescope error sources by means of numerical simulations. Additionally, a first laboratory experiment with a two-stages-APLC in the near-infrared (<i>H<i/>-band) is presented to further support the numerical treatment.<i>Results. <i/>Multistage configurations are found to be inappropriate to ELTs. The theoretical gain offered by a multistage design over the classical single-stage APLC is largely compromised by the presence of inherent error sources occurring in a coronagraphic telescope, and in particular in ELTs. The APLC remains an attractive solution for ELTs, but rather in its conventional single-stage configuration.