Micromechanical tunable Fabry-Pérot interferometers with membrane Bragg mirrors based on silicon/silicon carbonitride

This thesis adresses the design and fabrication of MEMS Fabry-Pérot interferometers for applications as tunable optical filters which can be operated over a broad spectral range.

To that end, silicon carbonitride is introduced as a new MEMS material which enables fabrication of large-area released membrane Bragg mirrors by vapour HF etching. Additionally, a new MEMS design with two released membrane mirrors is proposed in order to circumvent the limitation of its tuning range by pull-in found in standard MEMS FPIs.

Proof-of-principle devices are fabricated with application-relevant diameters up to 5 mm. Despite their large diameter, the devices exhibit an excellent parallelism between the membrane mirrors after the release with tilt deviations being only in the nanometer range. When actuated by DC voltages, the filters show an unprecedented spectral working range from 1.13 µm to 1.7 µm.