Optical Systems/MOEMS

Fabry-Pérot interferometer for sensor applications in the infrared spectral range on their way to further miniaturization

© InfraTec GmbH
FPI and detector in a TO39 housing. (by courtesy of InfraTec GmbH, www.InfraTec.de).
© Fraunhofer ENAS
Processed wafer.

The Fabry-Pérot interferometers (FPI) fabricated in Chemnitz are used for narrow band filtering of electromagnetic radiation in the visible and infrared wavelength ranges. The spectral range can be tuned continuously by electrical voltage. In particular for applications in the infrared range, very small, robust and inexpensive spectral sensors can be produced e.g. in combination with single-point detectors. Fraunhofer ENAS cooperates with the companies InfraTec GmbH Dresden, Jenoptik Optical Systems GmbH Jena and the Center for Microtechnologies of the Chemnitz University of Technology to achieve a further miniaturization of the MOEMS in a new FPI generation by an optimized and compact design. While maintaining a large optical aperture of 1.8 x 1.8 mm², the chip size of 7 x 7 mm² could be reduced to only 5 x 5 mm², so that 460 chips can be processed on a 6-inch wafer. By using an arrangement with two movable reflector carriers, the FPI distinguish themselves by a simple control with low voltage requirement and a good robustness against the influence of gravity. By adapting design parameters and the optical layer system, the working range of the filters can be adapted to customer-specific requirements. The entire spectrometer can now be accommodated in a TO39 housing. Applications of the miniaturized FPI can be found e.g. in mobile spectrometers for gas analysis in medical engineering, fabrication process control and safety technology.