Phase-driven pulse breaking during perfectly-matched second harmonic generation

A frequency-domain description of the second-harmonic generation by using laser pulses is presented. The influences of the pulse spectrum and of the crystal dispersion are taken into account which, for high intensities at perfect phase-matching, can produce stretching and eventually breaking of the pulse. A double autocorrelator has been constructed to monitor the pulse breaking during perfectly-matched second harmonic generation in a type I KDP crystal. A double passage inside the crystal was necessary to measure the nonlinear phase that the fundamental beam experiences during the first generation.