F. Guillot
J. Jarzynski
Georgia Inst. of Technol. Atlanta, GA 30332
E. Balizer
NSWC, Silver Spring, MD 20903
A two-beam laser Doppler vibrometer (LDV) is described, designed to measure the d[sub 33] electromechanical coupling coefficient for electrostrictive and piezoactive thin films. Optical fiber couplers are used to split the light into multiple beams and optical fibers are used to simultaneously illuminate the same spot on both sides of the film. The LDV measures the normal displacement on each side and the change in thickness of the film is determined from the algebraic sum of the two LDV signals. It is found that large bending motion of the film can lead to a significant error in the measured d[sub 33] coefficient. This is illustrated with data for PVF[sub 2] films and sources of this error are identified. The application of the LDV system to measure the large electrostrictive effect in polyurethane films is discussed. [Work supported by the Office of Naval Research.]