A beam operated MEMS variable optical attenuator

The microelectromechanical variable optical attenuator (VOA) using an electrostatic beam combined with a fiber-optic collimator has designed and fabricated. This VOA is based on silicon-on-insulator (SOI). When the driving voltage is applied to the beam and the substrate, the beam will yield a vertical displacement. Then the reflected light can't enter into the coupled fiber completely. Based on electrostatic actuation, the attenuation level is adjusted by changing the displacement of the beam. The relationship between the voltage and the displacement was analyzed by using ANSYS, a finite element analysis software package. The result of the simulation shows that the attenuator with the new structure has good performances. The fabrication steps use two wet etching processes. The active layer of SOI wafer is first patterned into the mirror sharp by TMAH, and the backside is etched to the buried oxide (BOX) using a 2-μm-thick SiO₂ mask. After releasing the structure in hydrofluoric acid, gold layers are deposited by vacuum evaporation. The testing is still in progress.