Current modulation and transient dynamics of single-mode semiconductor lasers under different feedback conditions

The authors study numerically the response of a single-mode semiconductor laser under modulation of the injection current in the presence of optical feedback, for different external cavity lengths and feedback reflectivities. For an external reflectivity larger than R_ext1.6×10^-4 feedback degrades the statistical properties of optical pulses considerably. When the external round-trip time is equal to the period of the modulation of the laser the optical pulses differ widely from each other and then they are not adequate for use in optical communication systems. In almost no case do we obtain better pulses than the corresponding ones in the absence of feedback. As happens in the solitary laser case, pattern effects, due to random sequences of inputs `0´ and `1´ bits, play an important role