Interferómetro de polarización para la caracterización mecánica de dispositivos piezoeléctricos

Piezoelectric devices are critical components in many different fields. They are often used as ultrasonic transducers, micro/nano positioners, and actuators. Electrical characterization of these devices can be performed by means of very well known techniques focused mainly on impedance measurements at different frequencies. However, since the measurement of mechanical properties corresponds to the determination of very small displacements, an optical interferometer is required. In this work, we propose the use of two coupled polarization interferometers for measuring the displacement of a mirror mounted in a piezoelectric device. The first one corresponds to a Michelson type interferometer with two orthogonally polarized branches. One of them is set as a reference, and the other changes its length as the piezoelectric under test is excited. Instead of forcing the interference of both branches with an analyzer, both signals are entered to a second polarization interferometer. This second interferometer consists mainly of a single birefringent crystal plate that provides a spatial interferogram. According to the phase change between reference and test signals, there is a uniform phase added to all of the points of the interferogram. We take advantage of this feature and of the stability of this second interferometer to recover the phase and the displacement of the mirror by means of very well known phase recovery methods.