Power evolution of an actively mode-locked AlGaAs semiconductor laser

Experimental observation and supporting theory on the power evolution of an actively mode-locked AlGaAs semiconductor laser (SL) under increasing bias current in the modulation range of 0.7-4.0 GHz are presented. It is shown that the useful bias current range in which solitary pulses are produced is limited by the pulse advancing within the modulation cycle with increasing bias current. An increase in the bias current allows threshold conditions to occur earlier, and the pulse advances to meet these conditions. The theory generalizes the coupling of the SL to the external cavity to include all values of the facet reflectivity. This results in two types of coupling-coherent coupling, which depends on both the SL and the external cavity state, and direct coupling, which depends solely on the external cavity state. The theory allows the coupling facet reflectivity to assume any value provided that the losses of the coupled system are small