Field stop diffraction and sampling effects in apodized pupil Lyot coronagraphs.

We study the predicted performance of two apodized pupil Lyot coronagraph designs in the presence of an occulter-plane field stop. We discuss techniques for capturing diffraction effects when the radius of the stop is larger than the field of view of an ordinary numerical diffraction model, including mask upsampling and analytical focal-plane envelope functions. We simulate a closed-loop coronagraphic wavefront control to assess the extent to which such diffraction effects can be compensated using deformable mirrors. We show that for the designs considered, field stop diffraction effects are significant at diameters considerably larger than the instrument field of view, suggesting the need to explicitly include a focal-plane stop in the design process.