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.