Femtosecond pulse synthesis by efficient second-harmonic generation in engineered quasi phase matching gratings.

We numerically design quasi-phase matched crystals with domains of arbitrary sizes for second harmonic generation by femtosecond pulses, taking into account both group velocity mismatch and dispersion. An efficient simulated-annealing algorithm is developed to design quasi- phase matching gratings which can yield the desired amplitude and phase of second-harmonic pulses in the presence of pump depletion. The method is illustrated with reference to single, double- hump and chirped fs Gaussian pulses in a lithium niobate crystal. (c) 2007 Optical Society of America