Mechanical stability of a latching MEMS variable optical attenuator

The mechanical stability of a latching shutter-insertion variable optical attenuator formed by deep reactive ion etching of bonded silicon-on-insulator (BSOI) is considered. The device can be continuously adjusted or latched into a discrete set of attenuation states using a rack-and-tooth mechanism. Simple numerical and analytic theories are developed to describe the effect of latching. The dynamics of the mechanism are characterized using internal actuation and it is shown that the use of a levered mechanism gives rise to several underdamped, low-frequency in-plane resonances during analog adjustment. Elastic nonlinearity is also identified. Vibration testing is then performed using an external piezoelectric transducer. It is shown that the effect of engaging the latch is to upshift the frequency of the most important mechanical resonance, reducing sensitivity to vibration in fixed attenuation states.