1. A. Yariv: In:Proc. 3rd Intern. Cong. Quantum Electronics (Columbia University Press, New York 1964), Vol. 2, pp. 1055–1064
2. R. Polloni, O. Svelto: IEEE J. Quantum Electr. QE4, 528 (1968)
3. It is not necessary to compare the duration of the pumping pulse with the intersystem crossing ratek ST , since it can be easily shown, with the help of (1b), thatk ST is related only to the equilibrium population of the triplet level and not to the time necessary to reach the equilibrium
4. Equation (1) are written under the assumption that the resonator mirrors are in contact with the active material, but the results obtained in steady state are valid, with the same parameters, also when this assumption is not satisfied. In fact it is obvious that the steady state properties of a laser do not depend on the distance of the mirrors from the active material
5. Topics in Appl. Phys.;F.P. Schäfer,1973