Interferometric interpretation for the degree of polarization of classical optical beams

We introduce an interferometric interpretation for the degree of polarization as a quantity characterizing the ability of a light beam to generate polarization modulation when it interferes with itself. The result is confirmed experimentally in Youngʼs interferometer with beams of controlled degree of polarization and by comparing to a standard polarimetric measurement. The new interpretation is a consequence of the electromagnetic interference law that we formulate for stationary, quasi-monochromatic, partially polarized light beams in time domain. Our work provides fundamental insight into the role of polarization in electromagnetic coherence and interference.