Characterization of polarization fluctuations in random electromagnetic beams

Two stationary, partially polarized electromagnetic beams with equal degrees of polarization may exhibit completely different time evolutions of the instantaneous polarization state. In this work, we derive a statistical quantity that describes the rate at which the field intensity in the beam, on average, is redistributed between the beam’s polarization state at any time and the state orthogonal to it. This method allows one to treat the dynamical properties of the polarization fluctuations both theoretically and experimentally. We demonstrate the method by applying it to important special cases, such as fields obeying Gaussian statistics, black-body radiation pencils and depolarized laser beams. We also prove that a geometric approach introduced earlier is closely connected with the present model. Radiation from all sources, whether natural or artificial, exhibits fluctuations of the electricfield strength and polarization state, due to either the inherent properties of the source or the randomness of the medium in which the field propagates. Thus, by measuring and characterizing the nature of these fluctuations, one can extract useful information about the source or the transmitting medium. The importance of the polarization fluctuations has been addressed in many theoretical and experimental studies, such as those on polarization mode dispersion in optical fibers [1, 2], particle shape determination [3], polarimetric radar imaging [4], physics of vertical-cavity surface-emitting lasers [5], atom–field interaction [6], supercontinuum 4 Author to whom any correspondence should be addressed. New Journal of Physics 11 (2009) 073004 1367-2630/09/073004+08$30.00 © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft