Relationship between degree of polarization and two-time degree of coherence of electromagnetic fields

For stationary light fields, the degree of polarization (DOP) of light relates to the maximum correlation between two arbitrarily decomposed orthogonal electric field components at a space–time point. We generalize this understanding theoretically by showing a physically insightful connection between DOP and the two-time degree of coherence of electromagnetic fields. Further, by using a variable path Mach–Zehnder interferometer, we experimentally demonstrate that the DOP of light can be directly determined by measuring the correlation between orthogonal electric field components at two-time points, showing an excellent match between the experiment and the theory. This study also leads to methods for constructing a tunable DOP source.