New simplified measuring method for distributed low-level birefringence

Abstract

This paper introduces the principle and execution of a new method for measuring of distributed minute birefringence based on simple polarimetry with phase-shifting method. The new method requires only three stepped photoelastic data although conventional phase-stepping methods require four or more. To evaluate the new method experimentally, two precise crystal wave plates having nominal retardation ± tolerance of 79.1±3.5 and 10.0±4.7 nanometers were used as specimens. The experimental averages of the distributed retardation in the specimens with standard deviations were found to be 80.2±15.0 and 18.8±7.06 nanometers. To estimate the measurement accuracy of the angular orientations of the distributed birefringence in the specimens, the angular positions of the rotation stage for the specimens were rotated intermittently 45 or 30 degrees at a time during the experiment. As a result, the averages of measured offsets of the angular orientations were found to be 30.1±8.14 for the specimen of 79.1 nanometers with standard deviations. It is concluded that the new method has potential of measuring for distributed minute birefringence.