  Absorption and dispersion of probe photons in the field of a high-intensity
circularly polarized laser wave are investigated. The optical theorem is
applied for determining the absorption coefficients in terms of the imaginary
part of the vacuum polarization tensor. Compact expressions for the vacuum
refraction indices and the photon absorption coefficients are obtained in
various asymptotic regimes of interest. The outcomes of this analysis reveal
that, far from the region relatively close to the threshold of the two-photon
reaction, the birefringence and dichroism of the vacuum are small and, in some
cases, strongly suppressed. On the contrary, in a vicinity of the region in
which the photo-production of a pair occurs, these optical properties are
manifest with lasers of moderate intensities. We take advantage of such a
property in the search of minicharged particles by considering high-precision
polarimetric experiments. In addition, Raman-like electromagnetic waves
resulting from the inelastic part of the vacuum polarization tensor are
suggested as an alternative form for finding exclusion limits on these
hypothetical charge carriers. The envisaged parameters of upcoming
high-intensity laser facilities are used for establishing upper bounds on the
minicharged particles.
