Simultaneous pumping into both the upper and the lower laser levels. Consider a laser transition between two upper energy levels E1 and E2 in an atomic system similar to that discussed in this section. Assume, however, that there is pumping up from the ground level into both the laser levels E1 and E2, at pumping rates R1 and R2, respectively. Assume there is also a lser signal Wsig on the 2 to 1 transition, as in this section.
Solve the steady-state equations for the population different delta N21=N2-N1 in this system, and put the answer into a form that illustrates the dependence on pumping rates and on signal saturation. Discuss briefly (a) the pumping-rate and relaxation-time conditions for obtaining an inversion at all in this system; and (b) the form of the signal saturation behavior, and how it compares to simpler systems.