Time-dependent simulation of a semiconductor laser amplifier: pulse compression in a ring configuration and dynamic optical bistability

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Abstract
We present a dynamic theory of a semiconductor laser amplifier with time-dependent optical input signal and driving injec- tion current. Previous treatments are extended by including a carrier density-dependent refractive index, a frequency-dependent gain, and multimode operation. The simulation yields optical bi- and tristability strongly depending upon the speed, at which the optical input-output characteristic is scanned. Tristability can he found in case of high pumping and large linewidth enhancement factor only. Applying our theory to a ring laser configuration we find asymptotic pulse compression, which can lead to the emission of a stable sequence of short pulses with widths down to about 6 ps. The face reflectivities, the external loss in the optical feedback loop, the detuning between the current repetition time and the optical round-trip time, the peak in- jection current, and the spectral linewidth of the gain are varied in order to check their influence on the optical pulsewidth. The shortest pulses are predicted for high optical feedback and low facet reflectiv- ities. Even with reflectivities as low as the pulsewidth is limited by the Fabry-Perot linewidth, rather than by the spectral gain line- width.