  Polarimetric experiments driven by the strong field of a circularly polarized
laser wave can become a powerful tool to limit the parameter space of not yet
detected hidden-photons and minicharged particles associated with extra U(1)
gauge symmetries. We show how the absorption and dispersion of probe
electromagnetic waves in the vacuum polarized by such a background are modified
due to the coupling between the visible U(1)-gauge sector and these
hypothetical degrees of freedom. The results of this analysis reveal that the
regime close to the two-photon reaction threshold can be a sensititive probe of
these hidden particles. Parameters of modern laser systems are used to estimate
the constraints on the corresponding coupling constants in regions where
experiments driven by dipole magnets are less constricted. The role played by a
paraphoton field is analyzed via a comparison with a model in which the
existence of minicharges is assumed only. For both scenarios is found that the
most stringent exclusion limit occurs at the lowest threshold mass; this one
being determined by a certain combination of the field frequencies and dictated
by energy momentum balance of the photo-production of a pair of minicharged
particles. The dependencies of the observables on the laser attributes as well
as on the unknown particle parameters are also analyzed.
