Advances in the control of Si substrates with magnetic smart materials to provide low-power surface control on the sub-nanometer level for space deformable mirrors

Accurate high-contrast imaging is achieved using deformable mirrors (DM) with actuator precision of 10s picometers. Beyond the demanding wavefront control requirements needed to achieve a contrast ratio of 10⁻¹⁰, there is an additional science driver for achieving this ratio over an outer working angle (OWA) large enough to image an exoplanet in a 1 AU orbit around a star 10 parsec or 0.1^′′ maximum separation from its host star. Using the formula OWA = Naλ/2D dictates that as D increases, the primary mirror diameter, so does the total number of actuator elements (Na²). Then, the demands of cabling, power, and mass also increase as Na², which is difficult to achieve for DM-based space missions. Furthermore, fixed-position actuators require high reliability. Our technology has the potential of being able to reduce the number of wires from Na² to 2Na and with a motion stage can mitigate the dead pixel issue. We report here our work to mature our technology which is based on magnetostriction and magnetization of a magnetic hard overcoat to enable maintaining in-plane stress and set-and-forget DM surface changes when actuators are powered off.