Evaluation of femtosecond pulse shaping with low-loss phase-only masks

We numerically and experimentally evaluate the performance of programmable femtosecond pulse shaping with specified time-dependent amplitude and phase profiles using phase-only masks. With the masks that have discrete phase levels of ≥4 designed by simulated annealing optimization algorithm, various pulses with arbitrarily specified amplitudes, pulsewidths, and pulse intervals are obtained with high accuracy. However, when specifying temporal phase profiles together with the amplitude, the range of shaped output pulses that can be produced with phase-only masks is somewhat limited even with a phase level of 64. The efficiency of transmitted optical power in the experiments is ∼60%, mainly due to the diffraction loss at a grating pair, which is much higher than that using an amplitude-and-phase mask.