Adaptive interferometer measurement of the piezoelectric and electro-optic coefficients of PZT films

摘要

In this paper we present simple interferometric technique for thin film testing with GaAs: Cr adaptive photodetectors based on the effect of the non-steady-state photoelectromotive force. The technique needs no special vibroinsulation and automatically adjusts and keeps the operation point of the interferometer. Two different interferometric schemes with GaAs:Cr adaptive photodetectors are reported. A modified Mach-Zehnder interferometer with adaptive photodetector is used for the measurement of piezoelectric coefficient of the thin film. A two-beam polarization interferometer with adaptive photodetector is used for the measurement of effective differential Pockels coefficient r_e = r_(33)-(n_0e)~3r_(13). It is shown that two-beam polarization technique allows measurement of the Pockels coefficient of thin film with a strong Fabry-Perot effect that usually presents in ferroelectric thin film. Strong hysteresis effect with a slightly asymmetric form of the hysteresis loop was observed at the dependence of d_(33) and r_e coefficients of the PZT thin film versus DC electric field. The values of d_(33) and r_e are in agreement with known data.