Second harmonic generation of femtosecond pulses at the boundary of a nonlinear dielectric

Using full vector Maxwell simulations we elucidate a fundamental source of temporal splitting of the second harmonic field generated by a femtosecond fundamental pulse under phase-mismatched conditions. One component of the g enerated field propagates at the second harmonic group velocity while the o ther is driven by the fundamental field and propagates at the fundamental g roup velocity. We analyze the conditions under which the temporal splitting should be observable.