A dynamic model of a gain-switched semiconductor laser amplifier
A semiconductor laser with one end facet coupled to the optical output of another laser is called a semiconductor laser amplifier. Initially, theoretical and numerical works on the SLA focused on its steady state properties, such as gain as a function of length and output power as a function of the power of the input signal, since applications were thought to be limited to long haul optical fiber communications and to improving the sensitivity of photodctectors by acting as preamplifiers. Later it was realized that the SLA could be used as bistable devices, which are used in optical computing and logic, and as a source of ultrashort optical pulses. These newfound applications demanded a substantial understanding of the dynamics of the SLA. Early models of the SLA have already discussed the existence of dynamic gain saturation, which produces desirable effects, such as pulse-shaping of subpicosecond pulses. However, the models vary with their applications, and hence, the assumptions made are not exactly the same. For example, Scholl discussed a gain-switched SLA used in producing picosecond pulses while Tohyama et al. discussed pulse-shaping in the SLA in the traveling wave amplifier (TWA) and reflecting wave amplifier (RWA) configurations.