A double-beam common path laser interferometer for the measurement of electric field-induced strains of piezoelectric thin films

We report in this paper the development of a modified Mach-Zehnder-type double-beam common path laser interferometer for the measurement of electric field-induced strain in piezoelectric materials, especially for the thin films. Compared to previous interferometers, this one is simpler and more compact, and the measurement and reference arms share a common path for most of the optical length. Example results have been reported for the quartz, lead zirconate titanate (PZT) ceramic sample, and PZT thin films. Double- and single-beam measurements have been carried out at different frequencies for the same spot of a PZT thin-film sample and it was found that the single-beam values were a few times of the values as obtained from the double-beam technique. This phenomenon is confirmed by the laser scanning vibrometer measurements.