  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 consider the case in which the
two-level laser is coupled to a vacuum reservoir via a single-port mirror and
seek to carry out our analysis by putting the noise operators associated with
the vacuum reservoir in normal order. It is found that the two-level laser
generates coherent light when operating well above threshold and chaotic light
when operating at threshold. Moreover, we have established that a large part of
the total mean photon number is confined in a relatively small frequency
interval.

Quantum Physics