Adaptive optimization of high harmonic generation

Summary form only given. We demonstrate that the intensity and spectral characteristics of high harmonics generated by an ultrafast laser can be optimized using shaped pulses to drive the process. Using an evolutionary strategy algorithm and a deformable mirror pulse shaper, the generation of a particular harmonic was enhanced by a factor of 4 beyond what can be obtained using a transform-limited driving pulse. We also demonstrate that a particular wavelength region can be spectrally selected by enhancing certain harmonics while suppressing adjacent harmonics. This ability is very important for certain application experiments, because other methods to spectrally select a particular harmonic can distort the ultrafast time structure of the harmonics. These data are preliminary because they were obtained using 30-fs laser pulses. We expect significant improvement in future by using 5 to 15 fs shaped laser pulses.