Tunable Double Membrane MEMS Fabry-Pérot Interferometers for the Near-Infrared

We present electrostatically actuated, surface-micromachined MEMS Fabry-Pérot interferometers with two released membrane mirrors. Actuation of the lower mirror towards the substrate allows resonance tuning over the full free spectral range of the 1
^st
interference order without the risk of reaching the pull-in point. We demonstrate a proof-of-concept device with a tuning range from 1130 nm to 1700 nm for actuation voltages below 10 V. Spatially resolved transmittance measurements show that the achieved spectral resolution is close to the expected theoretical value.