Large micromirror array for generating programmable slit masks for multi-object spectroscopy

摘要

Multi-object spectroscopy (MOS) is a powerful tool for space and ground-based telescopes for the study of the formationand evolution of galaxies. This technique requires a programmable slit mask for astronomical object selection.We are engaged in a European development of micromirror arrays (MMA) for generating reflective slit masks in futureMOS, called MIRA. The 100 x 200 μmsup2/sup micromirrors are electrostatically tilted providing a precise angle. The mainrequirements are cryogenic environment capabilities, precise and uniform tilt angle over the whole device, uniformity ofthe mirror voltage-tilt hysteresis and a low mirror deformation.A first MMA with single-crystal silicon micromirrors was successfully designed, fabricated and tested. A new generationof micromirror arrays composed of 2048 micromirrors (32 x 64) and modelled for individual addressing were fabricatedusing fusion and eutectic wafer-level bonding. These micromirrors without coating show a peak-to-valley deformationless than 10 nm, a tilt angle of 24° for an actuation voltage of 130 V. Individual addressing capability of each mirror hasbeen demonstrated using a line-column algorithm based on an optimized voltage-tilt hysteresis. Devices are currentlypackaged, wire-bonded and integrated to a dedicated electronics to demonstrate the individual actuation of allmicromirrors on an array. An operational test of this large array with gold coated mirrors has been done at cryogenictemperature (162 K): the micromirrors were actuated successfully before, during and after the cryogenic experiment. Themicromirror surface deformation was measured at cryo and is below 30 nm peak-to-valley.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.