A large-Travel vertical planar actuator with improved stability

We report achieving 3.9 microns of planar analog vertical travel in a robust electrostatically actuated polysilicon mid-infrared programmable diffraction grating. Typically, achieving such large travel would require prohibitively large gaps and actuation voltages. In order to reduce the actuation voltage and achieve greater travel before pull-in, we use thin beams and exploit stress-stiffening. Thin beams create stress management hazards because tensile stress in one layer can induce buckling in a lower layer. The problem with induced buckling has been solved with detailed attention to supports and their compliance. To make the device more robust against pull-in, the design incorporates a multi-layer nonlinear spring.