Abstract

Fluctuations in the amplitude, frequency, and polarization of the light emitted by semiconductor laser diodes limit the performance and reliability of many optical systems, such as communication links, optical radar, and optical disk read/write memories. Although it seems logical to explain this noise as random or stochastic, such erratic behavior can arise from completely deterministic models of lasers that retain the dynamics of the coherently induced polarization. This has been shown to be true for the simple model of a laser based on a two-level resonance, which results in the coupled Maxwell-Bloch equations. These equations are termed coherent because the Bloch equations describe, not only the inversion, but also the induced polarization of the gain media. The Maxwell-Bloch equations predict an array of instabilities and novel operation conditions for a laser: the output light may oscillate regularly or pulsate chaotically. Such behavior is not found in the incoherent population rate equation that adiabatically eliminated the dynamics of the polarization. However, the Maxwell-Bloch equations apply only to dilute materials in which the total gain is described by an ensemble average over many noninteracting molecules, such as gas lasers.

© 1987 Optical Society of America