Optical Phase Shift Measurements in Interferometry

Abstract

The precision and accuracy of optical phase-shifting technique is critical and affects the accuracy of the measurements undertaken using phase-shifting interferometers. The accuracy of optical phase shifters is limited by the inherent characteristics of the piezo-actuators (or PZT) such as nonlinearities, hysteresis, creep and thermal drift. This paper explores a new phase-shifting technique based on two acousto-optic modulators (AOMs) where the inherent characteristics of the PZT do not affect the required phase-shifts. The acousto-optic phase-shifting technique was successfully applied to control and measure the required optical phase shifts directly in the Mach-Zehnderinterferometer. This was accomplished by varying the phase delays between the two AOMs driving signals. In the experiment both Dual Trace and Lissajous Figures techniques were used to determine the behavior of the optical phase shifting system in terms of accuracy and repeatability.