Sub-nanosecond pulse dynamics of Nd:LSB microchip laser passively Q-switched by Cr:YAG saturable absorber

The pulse dynamics of a Nd3+:LSB microchip laser passively Q-switched by a Cr4+:YAG saturable absorber has been investigated experimentally and theoretically. A generalized model of a passively Q-switched microchip laser has been proposed. This model takes into consideration the thermalization and recombination of the activator atoms in the laser medium, the transverse inhomogeneity of the pump and laser beams and the finite saturable absorber recovery time. Very good agreement between theory and experiment has been obtained for a wide range of pump power with all combinations of output couplers and absorbers. The thermalization times of Nd3+ ions in LSB crystal have been estimated for the first time to the best of our knowledge: the thermalization time within the upper laser manifold is ∼0.4 to ∼0.8 ns, while within the lower laser manifold it is ∼0.2 to ∼0.5 ns.