Hi, many text about lasers introduces Q switching in detail and just mention gain switch briefly. We know the major difference b/w them is: Q-switching switches the loss from high to low while gain-switching switches the gain from low to high. But the time behavior is quite different in these two cases. In gain switching, does anyone know how to calculate the initial inversion of population when the photon starts to build up? and how to calculate the final inversion of population when the pulse just diminished to zero?