Interferometric measurements of electric field-induced displacements in piezoelectric thin films

Interferometric measurements of electric field-induced displacements in piezoelectric thin films using single-beam and double-beam optical detection schemes are reported. It is shown that vibrational response measured with a single-beam interferometer includes a large contribution of the bending motion of substrate. Therefore, it is difficult to apply single-beam technique for piezoelectric measurements in thin films. To suppress the bending effect a high-resolution double-beam interferometer is proposed. The sensitivity of the interferometer is significantly improved in comparison with previously reported system. The interferometer is shown to resolve small displacements without using a lock-in technique. An example of the interferometric capabilities is demonstrated with experimental results on electric field, frequency, and time dependences of piezoelectric response for quartz and Pb(Zr,Ti)O₃ thin film.