Quantum and quasiclassical lasing regimes

The Scully-Lamb quantum-mechanical laser theory is generalized to the case of active atoms situated in superposed upper and lower active states. In this case, a laser emits a field of nonzero average intensity. If there is no interference between the active levels of the active atoms, a state of the field may be found for which the average quantum-mechanical intensity is zero. An investigation is made of pumping in a molecular oscillator and in gas lasers. It is shown in which cases pumping causes interference between the active levels of the active atoms. An interference experiment which can distinguish between fields having zero and nonzero average intensities is discussed.