Modeling pulse shape of Q-switched lasers

A general approach describing the pulse shape and temporal width of Q-switched lasers has been derived. Based on a normalized intermediate variable describing the ratio of population inversion density at the beginning of Q-switch to that at threshold, a generalized characteristic equation that governs passively and actively Q-switched lasers is derived. From the characteristic equation, the pulse symmetry property and pulse width can be described and easily calculated for any given operating parameters, and the waveform of the laser pulse can be reconstructed without solving the laser rate equations. An approach is also given for the case of intracavity frequency-doubled Q-switched lasers. Theoretical results show agreement with experiments for a diode pumped Nd:YAG laser system that is passively Q-switched by a Cr⁴⁺ :YAG absorber