Micromachined optical tunable filter for long term stability gas sensors

A new component is presented: a tunable optical filter that can provide autocalibration of optical gas sensors and thus improve their long term stability. The device comprises three micromachined silicon wafers separated by two air gaps. It is shown that it can be applied as an electrically tunable Fabry-Perot filter, and used for the detection of gases that have spectral absorption bands in the infrared domain of wavelengths between 2 and 8 mu m. Calculations are performed to explain the mechanical and optical properties of the device under different applied voltages.