Dynamical modelling of measured time series from a Q-switched CO2 laser

The transient dynamics of a Q-switched CO2 laser is modelled quantitatively on the base of the four level model, a five dimensional nonlinear system of ordinary differential equations. Using the multiple shooting technique, internal parameters of the laser are estimated and the unobserved time courses of the population densities are constructed. For excitations barely above the laser threshold large pulse variations are identified as an effect of small variations of the pump parameter.