Pulse shortening by passive negative feedback in mode-locked train from highly-doped Nd:YAG in a bounce geometry

Investigation of pulse shortening by passive negative feedback in mode locked train from 2.4 at. % crystalline Czochralski grown Nd:YAG in a bounce geometry under QCW diode pumping is reported. For passive mode locking a semiconductor saturable absorber with 33 quantum wells grown on GaAa substrate acting also as nonlinear element for passive negative feedback by beam defocusing was used. Temporal diagnostics was performed with high speed digital oscilloscope with bandwidth of 9 GHz combined with fast photodiode which enabled direct observation of pulse shortening along extended pulse trains from single laser shot. Efficient pulse shortening from 120 ps in the beginning of the train to 35 ps for pulses at the end of the extended train containing more than 100 pulses was achieved.