Wavefront sensing using non-redundant aperture masking interferometry: tests and validation on Subaru/SCExAO

Recent evolutions in high contrast imaging have shed light on intrinsic limitations of general purpose adaptive optics (AO) systems. In particular, the low wind and petaling effects (LWE, PE), caused by the discontinuous apertures of telescopes, are poorly corrected, if at all, by commonly used wavefront sensors (WFSs). This results in large differential piston aberrations between the disjointed portions of the clear aperture. The LWE/PE decoheres the PSF core, generating multiple side lobes, and dramatically shuts off coronagraphic capabilities. We demonstrate the re-purposing of non-redundant sparse aperture masking (SAM) interferometers into low-order WFSs complementing the high-order pyramid WFS, on the SCExAO experimental platform at Subaru Telescope. The SAM far-field interferograms are used for direct retrieval of PE aberrations, which are invisible to the main AO loop. We show that this technique allows for a high-sensitivity, high-precision wavefront control loop, down to illuminations of a few hundreds of photons per frame.