The birefringence of materials is usually measured in the visible region with the use of a laser beam with the sample placed between crossed polarizers. Amplitude-division interferometers (ADIs) can also be used for birefringence measurements; however, the procedure is a bit more cumbersome, and they are not commonly used for this purpose. A mid-infrared polarization-division interferometer (PDI), recently developed in our laboratory, has been shown to provide novel applications and several advantages over amplitude-division interferometers. In this paper we demonstrate a novel approach to measuring infrared birefringence using the PDI developed in our laboratory. The proposed method is much simpler and may routinely be used for birefringence measurements on polymers, liquid crystals, and other oriented samples.
Prasad L. Polavarapu and Zhengyu Deng, "Polarization-Division Interferometry: An Approach to Birefringence Measurements," Appl. Spectrosc. 48, 1562-1564 (1994)