Simple undergraduate experiment for synthesizing and analyzing non-uniformly polarized beams by means of a Fresnel biprism

A simple scheme to synthesize non-uniform patterns of polarization across the transverse section of a beam is proposed with the standard materials in an undergraduate optics laboratory. The experiment is based on the superposition of two orthogonally polarized fields obtained by using a Fresnel biprism and dichroic polarizers. Although no interference pattern appears in the superposition area, a non-uniformly totally polarized field is synthesized. Analytic expressions for the Jones vector and Stokes parameters of the output beam are calculated and, in the process, students can cement their knowledge about the representation of polarized light with these formalisms. The experimental polarization pattern is either obtained from intensity measurements with a CCD camera or measured directly with a commercial polarimeter modified with a pinhole. This experiment will help students discover an easy way to vary the state of polarization across the transverse section of a light field.