Description: This project will develop and demonstrate an innovative microfabrication process to substantially improve the surface quality achievable in high-resolution continuous membrane MEMS deformable mirrors (DMs). Project specific aims include 2X improvement in small-scale surface flatness in comparison to the current state-of-the-art, and substantial reductions in sub-aperture scale diffractive losses due to actuator print-through, mirror scallop, and etch access hole scatter in continuous membrane MEMS DMs. Such wavefront control devices will fill a critical technology gap in NASA's vision for high-contrast, high-resolution space based imaging and spectroscopy instruments. Space-based telescopes have become indispensible in advancing the frontiers of astrophysics. Over the past decade NASA has pioneered coronagraphic instrument concepts and test beds to provide a foundation for exploring feasibility of new approaches to high-contrast imaging and spectroscopy. From this work, NASA has identified a current technology need for compact, ultra-precise, multi-thousand actuator DM devices. Boston Micromachines Corporation has developed microelectromechanical systems (MEMS) DMs that represents the state-of-the-art for scalable, small-stroke high-precision wavefront control. The emerging class of high-resolution DMs pioneered by the project team has already been shown to be compact, low-power, precise, and repeatable. These DMs can be currently produced with uncorrectable shape errors as small as 10nm root mean square (rms). These residual shape errors on the DM are mostly periodic and act essentially as a grating, producing diffraction spikes in the image plane. In the proposed project, we will develop processes and manufacturing innovations that collectively reduce or eliminate these shape errors through improved chemo-mechanical polishing, stress compensation film deposition, and elimination of etch access holes, resulting in a MEMS DM with unprecedented surface quality.

Benefits: There are many applications relative to NASA where there is a need for deformable mirrors with improved surface finish and quality over the current state-of-the-art. NASA needs include any ground or space based telescope or imaging system including TPF-C, TPF-I, EPIC and PECO. With the topography improvements proposed in this project, less light will be lost in the optical path, improving the effectiveness of all applications taking advantage of deformable mirrors.

There are applications relative to the requirements of government agencies and commercial markets which are in need of deformable mirrors with improved surface finish and quality over the current state-of-the-art. With these improvements, less light will be lost in the optical path, which will improve the effectiveness of all applications taking advantage of deformable mirrors. In addition, the following are specific targeted applications and how they are best suited for this development: 1)Astronomy/Surveillance: As telescopes and satellites search for more detail by collecting more light, the correction of atmospheric turbulence across the entire aperture remains important. 2)Optical communication: For long-range secure communication, large amounts of data can be sent over long distances using lasercomm systems. By improving surface finish, the amount of data transferred is increased due to enhanced error correction capabilities through the collection of more light. 3)Pulse-shaping: Pulsed lasers are used in a variety of applications from material characterization to laser marking and machining. The use of deformable mirrors allows scientists to better understand the composition of materials and allow manufacturers to make more precise, complex patterns. 4)Biological imaging: By improving the surface finish and quality, less light is scattered during transmission from the specimen to the collection device during imaging allowing for better resolution images.