Laser-noise suppression in the dressed-atom approach. II. Minimization principle for conventionally pumped lasers.

Abstract

The intrinsic property of laser systems with many internal degrees of freedom to generate a squeezed light is studied. The dressed-atom approach to fluctuations, described in the preceding paper [Khazanov, Koganov, and Shuker, Phys. Rev. A 48, 1661 (1993)], is employed. A minimization principle which governs noise quenching in laser systems is described comprehensively. This principle allows one to avoid complicated quantum-mechanical calculations to assess the squeezing capacity of the system. It is shown that noise in a laser system can be decomposed into noise states. These states interact coherently. For instance, each nonactive level in a multilevel lasing scheme may represent separate noise states under certain conditions while both lasing levels make only one noise state. The squeezing capacity of the system is determined by a quantity called the noise dimension. The theory is extended to laser schemes with many photons (two-photon generation, more than one lasing transition, etc.). The validity of the minimization principle is established for this type of system. Some consequences from the theory, which are relevant to the experiment, are discussed.