Stimulated emission by two-level atoms pumped to the upper level

We analyze the quantum properties of the light generated by a two-level laser in which the two-level atoms available in a closed cavity are pumped to the upper level by means of electron bombardment. We carry out our analysis by putting the noise operators associated with a vacuum reservoir in normal order. The normal ordering of the noise operators leads to normally-ordered quadrature and photon-number variance. It so turns out that the light generated by the two-level laser operating well above threshold is coherent and the light generated by the same laser operating at threshold is chaotic.