Dynamics and noise of fiber-grating semiconductor lasers affected by the line-width enhancement factor

Abstract

This paper numerically investigates the effect of the line-width enhancement factor on the dynamics and the intensity noise of InGaAs/InP lasers pumping in the wavelength of 980 nm at the strong optical feedback limit. The investigation is performed based on an improved time-delay rate equation model of a single-mode laser. The analyses are performed in terms of the temporal trajectory of the laser intensity, bifurcation diagram, relative intensity noise and injection current. The simulation results indicate that the laser, under strong optical feedback, mainly operates in CW, pulsation or chaos operation depending on the line-width enhancement factor and injection current values. At larger values of the line-width enhancement factor and injection current the pulsing operation becomes more dominant over wider range of strong optical feedback. The corresponding relative intensity noise level is close to or slightly larger than the level of the solitary laser noise. The optical feedback noise is found to be as low as the quantum noise level when the laser is operated in pulsing region and at larger values of the line-width enhancement factor and injection current.