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Correction of quasi static wavefront errors for ELTs: experimental validation of a two sequential DMs wavefront controller

Abstract 113

Submitted by Laurent PUEYO


L. Pueyo, J. Kay, N. J. Kasdin, M. McElwain, A. Give’on, S. Shaklan




Detection and spectral characterization of extrasolar planets with ELTs will require the ability to image very faint objects under a wide bandwidth. Such a goal implies the development of new exquisite wavefront control techniques in order to calibrate and correct both the amplitude and phase components of the residual quasi static halo that remains after the main AO loop. Here we focus on the correction stage of such a slow time scale AO loop. We report laboratory results that exhibit four important features of instrument responses sought for exo-planet characterization: post coronagraphic, high contrast, broadband, symmetric Point Spread Functions. This experiment was carried on the Princeton University high contrast testbed, equipped with a shaped pupil coronagraph and two sequential Boston Micromachines Kilo-DMs. In this paper we first review the theory and algorithms underlying one and two DM wavefront controllers and show why a second DM ultimately leads to better broadband performances. We then present an experimental validation of such a two DM amplitude and phase controller: we discuss how we generated a symmetric high contrast dark hole on our testbed, characterize its chromatic behavior and show that such a response is flatter than solutions obtained with a single DM.

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