Long-term stability and temperature variability of Iris AO segmented MEMS deformable mirrors

Abstract

Long-term stability of deformable mirrors (DM) is a critical performance requirement for instruments requiring open-loop corrections. The effects of temperature changes in the DM performance are equally critical for such instruments. This paper investigates the long-term stability of three different Iris AO PTT111 DMs that were calibrated at different times ranging from 13 months to nearly 29 months prior to subsequent testing. Performance testing showed that only a small increase in positioning errors occurred from the initial calibration date to the test dates. The increases in errors ranged from as little as 1.38 nm rms after 18 months to 5.68 nm rms after 29 months. The paper also studies the effects of small temperature changes, up to 6.2{\deg}C around room temperature. For three different arrays, the errors ranged from 0.62-1.42 nm rms/{\deg}C. Removing the effects of packaging shows that errors are $\le$0.50 nm rms/{\deg}C. Finally, measured data showed that individual segments deformed $\le$0.11 nm rms/{\deg}C when heated.