Bulk-micromachined tunable Fabry-Perot microinterferometer for the visiblespectral range

The design, fabrication and measured characteristics of a bulk-micromachine d tunable Fabry-Perot microinterferometer (FPMI) for the visible spectral r ange are presented. The FPMI is formed by two parallel 40 nm thick silver m irrors supported by a 300 nm low tensile stress silicon nitride membrane wi th a square aperture (side length of 2 mm) and initial cavity gap of 1.2 mu m. One of the mirrors is fixed, the other is under tension on a movable Si frame, which is electrostatically deflected, using several distributed ele ctrodes, to control cavity spacing and mirror parallelism. Performance achi eved is: high flatness of the mirrors (lambda/10 for the visible part of th e spectrum), low control voltages (< 21 V for 450 nm deflection) and simple fabrication. (C) 1999 Elsevier Science S.A. All rights reserved.