Resolution analysis method of retardance measurement instrument

The wave plate is an indispensable optical element for transforming polarization state in various optical fields. In the retarder's applications, precise measurement of the retardance is necessary. However, there is no common and effective way to analyze resolution of the retardance measuring instrument. For ensuring the retardance measurement accuracy, an analysis method involving a wedge wave plate with a tiny angle between two planes is proposed to characterize the resolution. The retardance of the wedge wave plate varies linearly and slightly due to its linear and diminutive variation of thickness. The diminutive variation of retardance versus displacement can be measured when the instrument has enough resolution. And the instrument demonstrates higher resolution when it can measure smaller retardance variation. In the experiment, a wedge wave plate is mounted on a two dimensional stage and its one surface is normal to the detecting light of the instrument. And then the retardance is measured along one certain direction and the results are fitted linearly. The method can be used to evaluate the resolution differences of retardance measurement instruments. The gained resolution of both two instruments is superior to 0.1nm. Through several experiments, it can be demonstrated that the proposed analysis method has the advantages of easy operation, high efficiency and simple configuration.