NASA’s SBIR topic S2.01 Proximity Glare Suppression for Astronomical Coronagraphy expresses specific interest in proposals for process improvements needed to improve performance of current wavefront correction devices. We propose to develop a manufacturing process for microelectromechanical deformable mirrors (MEMS DMs) that eliminates high spatial frequency topography due to print-through. In NASA's extreme wavefront control systems used for space-based coronagraphy, topography needs to be at or below 1nm rms to avoid being a limiting factor in achievable dark hole contrast. High spatial frequency topography on MEMS DMs can inhibit high contrast imaging in coronagraph systems through undesired diffraction. In previous work we have developed a clear, quantitative understanding of the root causes and sources of high-spatial frequency shape errors in MEMS DMs, and have demonstrated feasibility of one promising approach to eliminate those errors. The proposed new process involves modifications of the annealing processes, sacrificial materials specifications, layer thicknesses, and processing procedures used in MEMS foundry-based fabrication of DMs, and will lead to production of DMs with surface figure errors measuring 1nm rms, about an order of magnitude lower than the current commercial state-of-the-art. We will conduct experiments on test structures to optimize topography-reducing techniques while simultaneously ensuring high yield. By combining recent process innovations that improve topography with other recent innovations that markedly increase manufacturing yield, we will create a path toward producing ultra-smooth, high-yield MEMS DMs that will become enabling components for the space-based coronagraphs that NASA is relying on in its mission to search for habitable exoplanets.
Deformable mirrors with reduced high spatial frequency topography have a few astronomical NASA commercial applications. There are a number of missions/mission concepts that require the wavefront control provided by the proposed high-actuator-count deformable mirrors. These include the Large UV/Optical/Infrared Surveyor (LUVOIR), the Habitable Exoplanet Observatory (HabEx), Alpha Centauri Exoplanet Satellite (ACESat), and the Centaur pathfinder mission.
Deformable mirrors with reduced topography have non-NASA commercial applications:
Ground-based astronomy: Installations such as the Magellan Telescope and the planned ELTs.
Space surveillance and optical communications: Funded by Department of Defense, these have classified agendas.
Microscopy: Modalities affected include multi-photon fluorescence and localization microscopy techniques.