OPTICAL FEEDBACK EFFECTS ON THE SPECTRAL LINEWIDTH OF SEMICONDUCTOR-LASER SENSORS USING SELF-MIXING INTERFERENCE

The spectral characteristics of a semiconductor laser are significantl y affected by optical feedback in the active cavity of the diode, In t his paper, the influence of weak optical feedback on the linewidth is examined and a new relationship proposed. Feedback-induced changes in the power spectral density are also determined by a theoretical analyt ical model, in good agreements with experiments. These results are the n discussed for sensing applications using self-mixing interference, a s the maximum range of distance and displacement sensors can be limite d by half the coherence length of the laser diode modified by the opti cal feedback.