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Thermomechanical design, hybrid fabrication, and testing of a MOEMS deformable mirror

: Reinlein, Claudia; Appelfelder, Michael; Gebhardt, Sylvia; Beckert, Erik; Eberhardt, Ramona; Tünnermann, Andreas


Journal of micro/nanolithography, MEMS and MOEMS 12 (2013), No.1, Art. 013016, 11 pp.
ISSN: 1537-1646
ISSN: 1932-5150
ISSN: 1932-5134
Journal Article
Fraunhofer IOF ()
Fraunhofer IKTS ()
deformable mirror; unimorph; laser-induced deformation; thermally-induced deformation; homogeneous loading; compound loading

This paper reports on the thermomechanical modeling and characterization of a micro-opto-electro-mechanical systems deformable mirror (DM). This unimorph DM offers a low-temperature cofired ceramic substrate with screen-printed piezoceramic actuators on its rear surface and a machined copper layer on its front surface. We present the DM setup, thermomechanical modeling, and hybrid fabrication. The setup of the DM is transferred into a thermomechanical model in ANSYS Multiphysics. The thermomechanical modeling of the DM evaluates and optimizes the mount material and the copper-layer thickness for the loading cases: homogeneous thermal loading and laser-loading of the mirror. Subsequently, the developed and theoretically optimized DM setup is experimentally validated. The homogeneous loading of the optimized design results in a membrane deformation with a rate of -0.2 µm K-1, whereas the laser loading causes an opposed change with a rate of -0.2 µm W-1. Therefore, the proposed mirror design is suitable to precompensate laser-generated mirror deformations by homogeneous thermal loading (heating). We experimentally show that a 35-K preheating of the mirror assembly compensates for an absorbed laser power of 1.25 W. Therefore, the novel compensation regime "compound loading" for the suppression of laser-induced deformations is developed and proven.