  Starting from Maxwell equations for media with no-stationary linear and
nonlinear polarization, we obtain a set of nonlinear Maxwell amplitude
equations in approximation of first order of the dispersion. After a special
kind of complex presentation, the set of amplitude equations was written as a
set of nonlinear Dirac equations. For broad-band pulses solitary solutions with
half-integer spin and finite energy are found. The solutions correspond to
electromagnetic wave with circular Poynting vector and zero divergence. These
invisible for detectors waves are called dark states and the localized energy
we determine as electromagnetic mass.
