Theoretical study of optical pump process in solid gain medium based on four-energy-level model

A semiclassical algorithm is explored to a four-energy level model, aiming to find out the factors that affect the dynamics behavior during the pump process. The impacts of pump intensity Omega(p), non-radiative transition rate gamma(43) and decay rate of electric dipole delta(14) are discussed in detail. The calculation results show that large gamma(43), small delta(14), and strong pumping Omega(p) are beneficial to the establishing of population inversion. Under strong pumping conditions, the entire pump process can be divided into four different phases, tentatively named far-from-equilibrium process, Rabi oscillation process, quasi dynamic equilibrium process and 'equilibrium' process. The Rabi oscillation can slow the pumping process and cause some instability. Moreover, the duration of the entire process is negatively related to Omega(p) and gamma(43) whereas positively related to delta(14).