Passively mode-locked YAG:Nd laser with a negative feedback loop based on a high-current photomultiplier

A passively mode-locked YAG:Nd laser was built. It was provided with a negative feedback loop based on a high-current photomultiplier. Trains of picosecond pulses were generated and the duration of these trains was several tens of microseconds. When steady-state operation was reached, the feedback loop was disconnected and a short train of picosecond pulses with an overall duration of ~ 100 ns and an energy 1.5 mJ was generated. The energy stability of a second harmonic generated by such a short train was ± 1.5% when the efficiency of conversion to the second harmonic was low.