A second-quantized theory of the radiation field is used to study the origin of the excess noise observed in gainguided amplifiers. We find that the reduction of the signal-to-noise ratio is a function of the length of the amplifier, and thus the enhancement of the noise is a propagation effect arising from longitudinally inhomogeneous gain of the noise rather than from an excess of local spontaneous emission. We confirm this conclusion by showing that the microscopic rate of spontaneous emission into a given non-power-orthogonal cavity mode is not enhanced by the Petermann factor. In addition, we illustrate the difficulties associated with photon statistics for this and other open systemsby showing that no acceptable family of photon-number operators corresponds to a set of non-power-orthogonal cavity modes.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of the Optical Society of America B: Optical Physics|
|State||Published - Jun 1991|
ASJC Scopus subject areas
- Statistical and Nonlinear Physics
- Atomic and Molecular Physics, and Optics