Hi At continuous-wave oscillation the gain is equal to the threshold gain, i.e. g = gthreshold. Now in my book, I have the following expression for the steady-state population-inversion for a three-level laser N2, steady state - N1, steady state = (P-Γ12)/(P+Γ12)NT where NT=N1, steady state+N2, steady state, P is the pump rate and Γ12 is the rate at which level 2 decays into level 1. Now my question is: If at CW-oscillation g=gt, then why is it that we can change N2, steady state - N1, steady state (and thereby the gain) in a three-level laser at steady-state? Isn't this a contradiction?