Performance study of integrated coronograph-adaptive optics designs

Direct imaging of exo-planets requires that an efficient starlight suppression system and wavefront compensator work together to achieve a stable null whose contrast level is deep enough. The performances of several configurations for these two sub-systems have been extensively studied over the past few years, with particular attention being paid to the following four quantities and their relationship: throughput, contrast level, Inner Working Angle and bandwidth. In this paper we propose a new approach that considers starlight suppression and wavefront correction as a unique integrated component that is the association of a shaped-pupil and two sequential deformable mirrors that operate simultaneously as a short stroke pupil mapping device and a wavefront compensator. To do so we first develop a new method based on Huygens wavelets to explain the contrast limits of pupil mapping due to propagation, and study the hybrid associations of PIAA systems and shaped pupils that have been introduced in order to mitigate these effects. Then, since two cascaded deformable mirrors are also a wavelength independent amplitude actuator, we argue that they could be used in conjunction with shaped pupils to carry some of the apodisation load and thus increase the throughput of the new hybrid system.