  We present results for the photon spectrum emitted in non-linear Compton
scattering of pulsed ultra-strong laser fields off relativistic electrons for
intensities up to $a_0\gtrsim 100$ and pulse lengths of a few laser cycles. At
ultrahigh laser intensity, it is appropriate to average over the sub-
structures of the differential photon spectrum. Supplementing this procedure
with a stationary phase approximation one can evaluate the total emission
probability. We find the photon yield in pulsed fields to be up to a factor of
ten larger than results obtained from a monochromatic wave calculation.
