Wide range electrostatic MEMS Fabry Perot optical tunable filter: modelling an electrostatic and mechanic beam deflection

A novel wide range electrostatic microelectromechanical system floating Fabry Perot optical tunable filter (MEMS f-FPOTF) is modelled and analyzed in terms of its electro-mechanic behaviour. The composite beam approach has been used to model the floating Fabry Perot cavity. The floating dual membrane FPOTF consists of multi layer Si/SiO₂/Si thin films with an optical cavity in the middle structure. The filter tuning range has been improved by utilizing bonded silicon on insulator wafers that permits the floating cavity to be deflected both ways; up and down. Electro-mechanic analysis shows a 7% (STRUCTURE1) and 5% (STRUCTURE2) difference between analytical and finite element modelling in which the 7% difference in light incident angle contributes to a 0.5 nm shift while the 5% difference in length of cavity indicates a 4 nm shift in MEMS f-FPOTF operating wavelength. This analysis validates the analytical modelling of this device as a wavelength selector in coarse wavelength division multiplexing.