A Tunable Fabry-Perot-Interferometer for 3 - 4.5 μm Wavelength with Bulk Micromachined Reflector Carrier

摘要

This contribution deals with design, fabrication and test of a micromachined first order Fabry-Perot-Interferometer (FPI) usable as tunable infrared filter in a spectrometer. The approach discussed here minimizes mirror curvature by using relative thick (300 μm Si ) mirror carriers for the fixed and the movable mirror of the FPI. We use thermally grown λ/4 thick SiO_2 for antireflection layer at the mirror back side and for the first low refractive layer followed by a λ/4 thick polycrystalline silicon high refractive layer. Second and third λ/4 layer pairs of SiO_2 and polycrystalline silicon complete the mirrors. The cavity size is electrostically tuned and capacitively detected by a closed loop control.