Segmented micro deformable mirror with large stroke and low PV flatness

Segmented micro deformable mirrors offer advantages in size, weight, speed and performance over the continuous micro deformable mirrors and have tremendous potential in reducing the cost and weight of adaptive optical systems. But existing experimental segmented micro deformable mirrors still suffer from two defects: unacceptable PV (peak-to-valley) value and it is not applicable to infrared spectrum. We aim to present a preliminary solution of the PV value problem and report some progress toward solution of the infrared spectrum problem. ANSYS model of bilayer plate is built and the residual-stress-induced out-of-plane deformation of polysilicon plate with patterned gold layer is studied. A biaxial and uniform residual stress is established via an equivalent fake thermal load. The result of numerical analysis shows that under given residual stress of gold layer, there is an optimal gold pad size to get a minimum peak-to-valley mirror flatness that is just about acceptable. Furthermore, in order to expand the stroke or working range of the segmented micro deformable mirror, nonlinear beam is introduced into the structure design of it. Finally, by using already available surface fabrication foundry, the structure design is implemented to realize the segmented micro deformable mirror with a somewhat larger stroke, which is not yet sufficiently large to remove the defect of not being applicable to far infrared spectrum.