Adaptively shaped, sub-picosecond pulses at 3.4μm are obtained from a synchronously pumped optical parametric oscillator based on periodically poled lithium niobate. A simulated annealing algorithm is used in a learning loop to gain adaptive control of the mid-infrared idler pulse shape via shaping of a chirped near-infrared pump pulse. Both indirect control, via optimization of the signal average power, and direct control, via optimization of the two-photon absorption of the idler in an InGaAs detector, has been demonstrated. Both these optimization parameters lead to compressed idler pulses, with slightly differing pulse shapes. By optimization of the cross correlation signal in an interferometer with unequal arm lengths we are also able to deliver compressed double pulses with a variable time delay.
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