Solving functional reliability issue for an optical electrostatic switch

In this paper, we report the advantage of using AC actuating signal for driving micro electro mechanical systems actuators instead of DC voltages. The study is based upon micro mirror devices used in digital mode for optical switching operation. When the pull-in effect is used, charge injection occurs when the micro mirror is maintained in the deflected position. To avoid this effect, a geometrical solution is to realize grounded landing electrodes which are electro-statically separated from the control electrodes. Another solution is the use of AC signal which eliminates charge injection particularly if a bipolar signal is used. Long-term experiments have demonstrated the reliability of such a signal command to avoid injection of electric charges.