Effects of optical feedback on the light-current characteristics of semiconductor lasers

Theoretical and experimental investigations of the continuous wave (CW) output-power current characteristics of semiconductor lasers with optical feedback are reported. An analytical expression is presented which accounts for the external reflection in the form of an effective facet reflectivity. The coherence properties of the compound cavity laser field are incorporated by the correlation function of the optical field. An experimental setup was established to adjust and to control for different feedback levels. The normalized threshold current variation, due to feedback shows a dependence on the laser structure. This results from different confinement factors of the various waveguide structures. Up to reflection levels well within the coherence collapse regime the change of the slope of the light versus current curve is higher than calculated from incoherent feedback.<
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