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Proceedings Paper

Micromirrors for multiobject spectroscopy: optical and cryogenic characterization
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Paper Abstract

We are developing micromirror arrays (MMA) for future generation infrared multiobject spectroscopy (MOS) requiring cryogenic environment. So far we successfully realized small arrays of 5×5 single-crystalline silicon micromirrors. The 100μm ×200μm micromirrors show excellent surface quality and can be tilted by electrostatic actuation yielding 20° mechanical tilt-angle. An electromechanical locking mechanism has been demonstrated that provides uniform tilt-angle within one arc minute precision over the whole array. Infrared MOS requires cryogenic environment and coated mirrors, silicon being transparent in the infrared. We report on the influence of the reflective coating on the mirror quality and on the characterization of the MMA in cryogenic environment. A Veeco/Wyko optical profiler was used to measure the flatness of uncoated and coated mirrors. The uncoated and unactuated micromirrors showed a peak-to-valley deformation (PTV) of below 10nm. An evaporated 10nm chrome/50nm gold coating on the mirror increased the PTV to 35nm; by depositing the same layers on both sides of the mirrors the PTV was reduced down to 17nm. Cryogenic characterization was carried out on a custom built interferometric characterization bench onto which a cryogenic chamber was mounted. The chamber pressure was at 10e-6 mbar and the temperature measured right next to the micromirror device was 86K. The micromirrors could be actuated before, during and after cryogenic testing. The PTV of the chrome/gold coated mirrors increased from 35nm to 50nm, still remaining in the requirements of < lambda/20 for lambda=1μm.

Paper Details

Date Published: 13 February 2008
PDF: 10 pages
Proc. SPIE 6887, MOEMS and Miniaturized Systems VII, 68870B (13 February 2008); doi: 10.1117/12.764381
Show Author Affiliations
Severin Waldis, Univ. of Neuchatel (Switzerland)
Frederic Zamkotsian, Lab. d'Astrophysique de Marseille (France)
Patrick Lanzoni, Lab. d'Astrophysique de Marseille (France)
Wilfried Noell, Univ. of Neuchatel (Switzerland)
Nico de Rooij, Univ. of Neuchatel (Switzerland)

Published in SPIE Proceedings Vol. 6887:
MOEMS and Miniaturized Systems VII
David L. Dickensheets; Harald Schenk, Editor(s)

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