Authors: J.H. Chen, W. Weingar, A. Azarov and R.C. Giles
Affilation: Agere Systems, United States
Pages: 296 - 299
Keywords: MEMS, mirror, pull-in effect, stabilization
Recently proposed optical subsystems utilizing micro-electromechanical components are being developed for use in photonic crossconnects, optical add/drop multiplexers, and spectral equalizers. Common elements to these subsystems are electrostatically actuated micromechanical tilt mirrors that steer optical beams to implement the subsystem function. In these applications, voltages are applied to mirror elements to change the mirror-tilting angle, on one or two axes. Feedback control methods are commonly used to obtain precise mirror orientations to minimize loss through optical switch fabrics or to stabilize attenuation through spectral equalizers. However, the mirror tilt angle range is limited because of inherent instability beyond a critical tilt angle (snapdown angle), and the usual feedback schemes do not counteract this effect. This paper describes control methods to enable operation of electrostatically actuated mirrors beyond the critical tilt angle, yielding advantages including greater scalability of switch arrays and increased dynamic range of attenuators.