Pulsed generation in a combined-diode-pumped Nd3+ : Ca3Ga2Ge3O12 laser with a small jitter of the pulse repetition rate

Pulsed generation in a solid-state Nd3+:Ca3Ga2Ge3O12 (Nd:CGGG) laser (SSL) with passive Q-switching by the Cr4+:YAG crystal is studied. To reduce the pulse repetition rate jitter of the SSL generation, the current through a pump diode was combined from a constant component and short pulse. It is shown that if the sum of the constant and pulsed components of the optical pump power exceeds the threshold pump power by less than twice (1 < xp < 2), the pulse repetition rate jitter of the SSL generation has the local minimum, which is obtained when the constant component of the pump power relative to the threshold power is 2-xp. The natural lifetime τ of the upper level of the laser element (LE) in the SSL cavity is proposed to be measured by the delay of the SSL pulse with respect to the leading edge of the pump pulse. It is shown that the lifetime measured in this way is shorter than the time τ measured by the standard method in which the LE resides outside the SSL. At the laser pulse repetition rate of 192 Hz, the pulse energy of 3.5 μJ and duration of 11 ns, the relative jitter of the laser pulse period was ~0.06 %, which is by more than two orders of magnitude lower than that under a constant current through the pump diode.