Stochastic behavior of an external optically injected single-mode semiconductor laser including Langevin noise sources

Abstract

In this paper the stochastic dynamics of an optically injected semiconductor laser (SCL) operating in the single mode are theoretically and numerically investigated in the framework of the Langevin approach. Novel modified analytical expressions for relative intensity noise (RIN) and frequency noise have been developed for both master laser and slave. The effective gain coefficient (EGC) parameter of this rate-equation model allows noise suppression of 65 dB to be achieved in addition to the diminution of RIN spectra achieved by classic decisive parameters. A modified Schawlow–Townes formula is also proposed for laser linewidth. Moreover the induced modulation of the FWHM by the mean EGC allows more significant reduction of the laser linewidth, unlike those of classic SCLs when the EGC is lower than 0.5, opening the route to the ideal laser linewidth, which is discussed. The impacts of linewidth enhancement factor, spontaneous emission factor and EGC are investigated in noise spectra around the threshold current.