The commercial potential of micro-opto-electro-mechanical systems (MOEMS) has been more than adequately demonstrated, if not fully realized, with successful applications in projection display, optical switching for communications, and adaptive optics. Microfabrication processes are well suited to the manufacture of miniaturized optical components and systems. The principal advantage of microfabrication of optical components is low-cost batch fabrication of movable mirror elements with uniform operating characteristics. With commercially successful systems comprising over a million moving parts demonstrated several years ago, it is reasonable to ask why commercial MOEMS products are not already more widespread. One answer to this question is that the effect of materials properties on the optical performance of MOEMS has hampered successful development. For the most part designers have worked around the limitations of available thin film materials without developing adequate process control solutions. This chapter will examine the importance of materials properties, particularly residual stresses and residual stress gradients of thin films, for the design and performance of MOEMS. The effects of residual stress and residual-stress gradients on selected microfabricated optical systems will be examined in Sec. 12.2. Existing measurement techniques and the limitations of those approaches will be discussed in Sec. 12.3. Design approaches to mitigate the effects of residual stresses or employ them to advantage are described in Sec. 12.4. In Sec. 12.5 approaches to modeling and simulation of MOEMS will be briefly discussed.
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