A simple method to measure the thickness and order number of a wave plate

Thickness and order number are important parameters for a wave plate in optical experiments. However, the encapsulation of the wave plate makes its thickness difficult to measure directly. In this paper, we propose an indirect measurement method to obtain the thickness and order number of a uniaxial crystal wave plate. With this method only the maximum and minimum values of the optical power of the transmitted light through the wave plate are measured in the experiment by rotating the wave plate around its optical axis. This simple method is easy to realize in the college physics laboratory, and it is also of importance for students to further understand the underlying physics of the wave plates. (paper)