FEMTOSECOND PULSE SHAPING BY AN EVOLUTIONARY ALGORITHM WITH FEEDBACK

We report on computer controlled compression of femtosecond laser puls es using a programmable liquid crystal spatial light modulator which i s feedback-controlled by an evolutionary algorithm. This algorithm gen erates the optimal laser field on the basis of feedback from the exper iment by optimizing the laser pulse iteratively. Without knowledge of the (chirped) input pulses, the experimental signal (second harmonic l ight/SHG) is maximized by the algorithm, thus resulting in fully compr essed pulses. This method only makes use of the experiment's response (SHG signal) on the formed pulses. No other parameters need to be cons idered. This approach leads to many experimental applications in all f ields of optics and ultrafast spectroscopy where particularly shaped p ulses are advantageous.