MEMS Tunable Fabry-Pérot Filters for Infrared Microspectrometer Applications

Microspectrometers based on MEMS Fabry-Pérot (FP) interferometers as optical band-pass filters are a recently emerging solution. InfraTec is one of the leading suppliers of tunable infrared MEMS filters for gas analysis. Different FP filters for the wavelength range 3-11 µm were designed and fabricated. The FP reflector thin film design based on conventional optical thin films was introduced to cover the whole MWIR and LWIR range. Beside this, a completely new so-called Dual-Band design has been developed, in which the 1st interference order in the LWIR and the 2nd order in the MWIR can be used simultaneously. To compensate temperature drift and stabilize sensitivity against vibration two different solutions were engineered. Furthermore FP filters of higher orders are developed to decrease the spectral bandwidth up to 20 nm in the MWIR. Combined with PbSe detectors fast tunable FP devices have been created with both a high signal-to-noise ratio and a high spectral resolution for the detection of hydrocarbons.