Thinning-out in optimized pulse shaping method using genetic algorithm

An optical pulse shaping system using a spatial light modulator (SLM) controlled by genetic algorithm (GA) optimization was improved and we demonstrated that the time for finding the optimal condition could be shortened by a proposed “thinning out” method. In this method, GA controls only every N (N=1, 2, 4, 8, 16) pixel in the SLM. The conditions of the remaining pixels are derived by interpolation. The effectiveness of this method was verified by the pulse compression of chirped femtosecond pulses and the increase in the two-photon excitation efficiency of α-perylene crystals. The influence of the thinning out on the pulse shape is discussed, and an advanced method is proposed. It is shown that the disadvantages of the thinning out method can be compensated for by changing the value of N during optimization.