Abstract
Monolithic fabrication of continuous facesheet high-aspect ratio gold microelectromechanical systems (MEMS) deformable mirrors (DMs) onto a thermally matched ceramic-glass substrate (WMS-15) has been performed. The monolithic process allows thick layer deposition (tens of microns) of sacrificial and structural materials thus allowing high-stroke actuation to be achieved. The fabrication process does not require wafer bonding to achieve high aspect ratio three-dimensional structures. A gold continuous facesheet mirror with 3.4 nm surface roughness has been deposited on a 16 × 16 array of X-beam actuators on a 1-mm pitch. A stroke of 6.4 μm was obtained when poking two neighboring actuators. Initial electrostatic actuation displacement results for a high-aspect ratio gold MEMS DM with a continuous facesheet will be discussed. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. (DOI: 10.1117/1.JMM.12.3.033012)
Highlights
A monolithic fabrication process has been investigated for the development of a high-aspect ratio microelectromechanical systems (MEMS) deformable mirror (DM) for adaptive optics
Unlike current MEMS processes such as the Sandia Ultra-planar, Multilevel MEMS Technology[1] (SUMMiT) process, and the MEMSCAP PolyMUMPS2 process that limits a DM’s stroke due to the thin-film (2 μm) sacrificial layer used, the monolithic process described in this article has the ability to deposit thicker layers of structural and sacrificial materials
We have developed a high-aspect-ratio, monolithic process for fabricating a high-stroke MEMS DM
Summary
A monolithic fabrication process has been investigated for the development of a high-aspect ratio microelectromechanical systems (MEMS) deformable mirror (DM) for adaptive optics. The actuators consist of square 400 × 400 μm membranes supported diagonally at the corners by four 390 × 20 μm fixed-guided beams.[5,6] When the actuators are displaced by more than half the thickness of the spring layer, they become nonlinear. This in turn allows mechanical “strain stiffening” to increase the travel range.[7] The actuator can be described by a nonlinear spring equation near pull-in: Fm 1⁄4 kδ[3]; ðNonlinear spring equationÞ (1). The pull-in voltage is found by substituting δ 1⁄4 ð3∕5Þg into Eq 2 leading to Vpi 1⁄4 1⁄2216 kg5∕3125 ε0A1∕2
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