Active optical structures by use of PZT thick films

Piezoceramic thick films offer the possibility of integrated solutions for microsystems applications. The authors have developed a screen printable thick film paste based on a low sintering PZT-PMN formulation. It shows excellent dielectric and electromechanical properties on microelectronic substrates like ZrO2, Al2O3, silicon and low temperature cofired ceramics (LTCC). As the authors found out by experiments, properties of the PZT thick film structures are strongly influenced by the size of the active areas. As the active area becomes smaller dielectric as well as electromechanical properties are reduced. The paper illustrates application of PZT thick films for active optics. A deformable mirror based on a Si wafer with 150 mm diameter was prepared by screen printing 91 honeycomb thick film PZT actuators with 80 micron thickness at the backside of the wafer. Optical aberrations like astigmatism and trefoil could be calculated by finite element modeling and are demonstrated by experiment. The combination of cantilever structures based on PZT thick films with solid hinges and platforms for optical devices enables for active systems with two or more degrees of freedom in deformaton. Two examples of moveable holders for a FAC lens and a reflecting mirror have been demonstrated. Up and down movements as well as more complex deformations like tilting and twisting could be achieved by simultaneous or alterning driving of two or three cantilever structures.