The two-dimensional array of 2048 tilting micromirrors for astronomical spectroscopy

In multi-object spectrometers, field selectors, which are located in the focal plane of the telescopes, are required for the selection of astronomical objects, such as stars or faint galaxies. We present a two-dimensional micromirror array as a field selector. Object selection is achieved through the precise tilting of micromirrors, which reflect the light of objects toward the spectrometer. These arrays were composed of 2048 (32 x 64) electrostatically actuated silicon micromirrors that measured 100 x 200 mu m(2). The micromirrors were addressed either by lines or individually using a line-column addressing scheme. The fabrication process of these devices involved three wafers and two wafer-level bondings. Characterization, by white light interferometry, revealed a tilt angle of 25 degrees at a voltage of 121 V, and a coated micromirror deformation below 10 nm. A fill factor of 82% and a contrast of 1000:1 were also observed. Demonstration of the line-column addressing scheme was achieved through its application to a sub-array of 2 x 2 micromirrors.