Cryogenic wavefront correction using membrane deformable mirrors

Micro-machined membrane deformable mirrors (MMDMs) are being evaluated for their suitability as wavefront correctors at cryogenic temperatures. Presen ted here are experimental results for the change in the initial mirror figu re of 37-channel MMDMs from OKO Technologies upon cooling to T=78K. The cha nges in the influence functions are also explored. Of the sample of 3 mirro rs tested, one was found to have sufficiently small initial static aberrati ons to be useful as a wavefront corrector at this temperature. The influenc e functions at T=78K were found to be similar in shape to both those at roo m temperature and theoretical predictions of the MMDMs surface shape. The m agnitude of the surface deflection at T=78K was reduced by around 20% compa red with room temperature values. (C) 2001 Optical Society of America.