Applications of TiNi thin film shape memory alloys in micro-opto-electro-mechanical systems

The application of shape memory alloy (SMA) thin films in optical devices i s introduced and explored for the first time. Physical and optical properti es of titanium-nickel (TiNi) SMA thin films change as these films undergo p hase transformation upon heating. An optical beam can be modulated either m echanically using a TiNi actuator or by the changes that occur in TiNi's op tical properties upon heating and phase transformation. Reflection coeffici ent of TiNi films were measured in their martensitic (at room temperature) and austenitic (elevated temperature) phases. The reflection coefficient of the austenitic phase were higher than those of the martensitic phase by mo re than 45% in the wavelength range between 550 and 850 nm. A microfabricat ed TiNi diaphragm with a 0.26-mm-diameter hole was used as a prototype ligh t-valve. The intensity of the transmitted light through the hole was reduce d by 10-17% when the diaphragm was heated. (C) 1999 Elsevier Science S.A. A ll rights reserved.