title: Optical anisotropy induced by resonant absorption or amplification of radiation.
abstract: When a light beam propagates through an ensemble of two-level quantum systems, the resonant interaction between these systems and the radiation field may be described by a complex susceptibility. Even if the medium is of a type ordinarily considered isotropic, the susceptibility will be a tensor. In this paper, explicit expressions for the elements of this tensor are derived from quantum-statistical mechanics. A physical explanation of the induced anisotropy is given, and the experimental conditions under which it can be neglected are described.
authors.forename: J D
authors.initials: JD
authors.lastname: Macomber