Complex dynamics of passively Q-switched microchip laser

The laser-diode-pumped 1.5 μm multimode passively Q-switched Er,Yb:YAl3(BO3)4 microchip laser with a saturable absorber of Co2+:MgAl2O4 was studied experimentally. The maxim repetition rate of 81.25 kHz was obtained with output energy of 2.99 μJ and pulse duration of 10.8 ns. The complex dynamics was found with the increase of pumping power: from 3 W to 9.4 W, five regions with complex multimode dynamics and five others with simple dynamics were found, and they appeared alternately. In the regions with multimode dynamics, the clear antiphase phenomenon of pulses with different modes was observed at the beginning, and then the dynamics of laser pulse train tends to be more complex. The phenomenon is very similar to the self-similarity of typical nonlinear dynamical systems.