Lasers quasi-stationary inversion

I 1.6.3. Quasi-Stationary Inversion in Collisional Gas-Discharge Lasers, Excitation by Long-Lifetime Particles and Radiative Deactivation... 

The time profile of the laser pulse is not only determined by the amplification per round trip G t) (Vol. 1, Sect. 5.2) but also by the relaxation times t,-, Xk of the upper and lower laser levels. If these times are short compared to the rise time of the pump pulse, quasi-stationary laser emission is reached, where the inversion AN(t) and the output power FL(r) have a smooth time profile, determined by the balance between pump power Pp t), which creates the inversion, and laser output power Fl(0. which decreases it. Such a time behavior, which is depicted in Fig. 6.1a, can be found, for instance, in many pulsed gas lasers such as the excimer lasers (Vol. 1, Sect. 5.7). 

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