Stability analysis for grating-tuned strong-external-feedback semiconductor lasers

We give a simple stability analysis within the scope of steady-state solution for the grating-tuned strong-external-feedback semiconductor lasers. In our model, a fluctuation in the refractive index of an active medium through the coupling of carrier density will cause another fluctuation in the refractive index. If the latter is always smaller than the former, the fluctuation will be damped, and therefore the corresponding operating point of the laser is stable. Our analysis indicates that there are various stable and unstable operating-frequency ranges for various reflectivities of the internal facet of the laser diode. In addition, it agrees well with the experimental results and explains the bistability of threshold gain versus operating frequency.