Optical systems/MOEMS

MEMS components with subwavelength structures for infrared applications

© Fraunhofer ENAS
Photographic image of a MEMS chopper for infrared radiation.
© Fraunhofer ENAS
SEM view of a part of the used membrane with subwavelength structures that is used as top layer of this component.

The use of sub-wavelength structures is an alternative way for functionalizing optical surfaces in contrast to the application of optical layers or layer stacks. Highly reflecting surfaces, wavelength filtering surfaces, surfaces with extremely low reflectance and highly absorptive surfaces can be achieved. In many cases, only one single layer of a metal or of a dielectric material is applied to form the sub-wavelength structures. Nano structuring by nano imprint lithography recently opened the way for the commercial application of principles using subwavelength structures and plasmon related optical effects for volume fabrication of these components. Nano imprint lithography is also compatible to other processes, which are needed to fabricate complex MOEMS components, such as MEMS and MOEMS fabrication technology sequences. Tunable spectrum filters and shutters are key components of such hyperspectral imaging systems next to the detector arrays. These novel components can turn infrared imaging into spectral and hyperspectral imaging, which enables the gathering of substantially more information in comparison to single spot spectrum recording and regular wideband infrared imaging.