Characterization of Large-Stroke MEMS Actuators for Adaptive Optics

Darwin Fernández 
 

Baskin School of Engineering, University of California, Santa Cruz

Mentor: Bautista Fernández

Advisor: Joel Kubby

Home Institution: Hartnell Community College 
 

Adaptive optics (AO) systems are used to reduce the effects of rapidly-changing optical distortions due to the Earth’s atmosphere. An important component of an AO system is the deformable mirror. Next-generation deformable mirrors will utilize Micro-Electro-Mechanical System (MEMS) actuators to pull the mirror’s shape to match the phase distortion and correct any aberrations. The goal of this project is to characterize various large-stroke MEMS actuator designs for the upcoming Thirty Meter Telescope. Two-dimensional actuator designs were created using a layout software program called L-Edit. A Finite Element Analysis software program, Intellisuite, was used to acquire a three-dimensional model of the actuator and to simulate its stroke at different voltages. The manufactured actuators were tested using probes to apply voltages and then a white-light interferometer was used to analyze their performance. Interferometric results show that these actuators pull-in at approximately one-third of the gap, as expected. However, the pull-in measured in the actuators differed from the results of the simulations. The deviations resulted from fabrication issues, such as layer-to-layer misalignment, excess residue, and variation of film thickness. The results of this work will permit the best actuators and mirror-boundary conditions to be utilized in the creation of an optimal AO MEMS deformable-mirror system.