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Fewer than 1% of all exoplanets detected to date have been characterized onthe basis of spectroscopic observations of their atmosphere. Unlike indirectmethods, high-contrast imaging offers access to atmospheric signatures byseparating the light of a faint off-axis source from that of its parent star.Forthcoming space facilities, such as WFIRST/LUVOIR/HabEX, are expected to usecoronagraphic instruments capable of imaging and spectroscopy in order tounderstand the physical properties of remote worlds. The primary technologicalchallenge that drives the design of these instruments involves the precisioncontrol of wavefront phase and amplitude errors. Several FPWS and controltechniques have been proposed and demonstrated in laboratory to achieve therequired accuracy. However, these techniques have never been tested andcompared under the same laboratory conditions. This paper compares two of thesetechniques in a closed loop in visible light: the pair-wise (PW) associatedwith electric field conjugation (EFC) and self-coherent camera (SCC). We firstran numerical simulations to optimize PW wavefront sensing and to predict theperformance of a coronagraphic instrument with PW associated to EFC wavefrontcontrol, assuming modeling errors for both PW and EFC. Then we implemented thetechniques on a laboratory testbed. We introduced known aberrations into thesystem and compared the wavefront sensing using both PW and SCC. The speckleintensity in the coronagraphic image was then minimized using PW+EFC and SCCindependently. We demonstrate that both SCC and PW+EFC can generate a dark holein space-like conditions in a few iterations. Both techniques reach the currentlimitation of our laboratory bench and provide coronagraphic contrast levels of5e-9 in a narrow spectral band (<0.25% bandwidth)

Comparing focal plane wavefront control techniques:\\Numerical simulations and laboratory experiments