Coherence properties of a semiconductor laser with feedback from a distant reflector - Experiment and theory

The visibility (the absolute value of the field-autocorrelation function) of a semiconductor laser subject to optical feedback is measured. The feedback was provided by a mirror at between zero and the maximum feedback, for which the laser still operated in a single longitudinal mode of the semiconductor chip. The results are compared with numerical solutions of the Lang and Kobayashi equations. Over the whole range of feedback agreement is noted between experiment and theory. However, this agreement requiers an unusually high value of the linewidth enhancement factor. The self-sustained noise model is found to yield an inaccurate description of the experiments. Suggestions are given to explain this inadequacy.