Theory of mode competition noise in semiconductor injection lasers

A theoretical analysis of the mode-competition noise in semiconductor injection lasers is given. The source of the noise is supposed to be fluctuations of the number of photons and electrons on optical emission, and is amplified by optical gain in which the mode-competition phenomena are taken into account. When a lasing mode jumps to another mode, noise becomes largest and shows
1/f^{\alpha}
characteristics on its frequency spectrum, where the index of
\alpha = 2
is theoretically obtained based on a perturbation analysis of the noise. The noise of an individual mode is in general larger than that of the overall lasing modes. The noise reduces to the level of the quantum noise when the laser operates either in single mode or in stable multimodes.