Phase noise in semiconductor lasers - A theoretical approach

A theoretical study is presented of intensity and phase noise in semiconductor lasers in view of the importance of such phenomena for the design of optical communications systems. Equations describing the deterministic evolution of the electromagnetic field intensity fluctuation and the instantaneous frequency deviation are first obtained, then Langevin noise terms are added to account for the randomness of the spontaneous emission events. Evaluation of the autocorrelation functions of the intensity and frequency deviations then results in the respective power spectral densities for the fluctuations, which are shown to be in good agreement with experimental measurements for a single-mode semiconductor laser.