  We analyze the development of pulse instability within non-linear
electrodynamics based on the Maxwell's equations, without the approximation of
slowly varying amplitudes and phases. The action is determined on the basis of
the logarithmic and exponential Lagrangians, built on the invariants of the
electromagnetic field. It is shown that the onset of the collapse of an
ultra-short pulse of the electromagnetic field in the framework of nonlinear
electrodynamics.
