Ultrashort pulse generation by gain switching

In this work, ultrashort pulse generation by gain switching in semiconductor lasers is modelled. The model is based on multi- mode rate equations which are numerically solved by using Runge-Kutta-Fehlberg method. Although the standard parameters are taken for 1.3 fim InGaAsP ridge-wavaguide laser, rate equations are derived in an extended form to be used in the modelling of any semiconductor laser. The important laser diode parameters such as gain compression, Auger recombination and nonradiative recombination are taken into account. In addition, parameters depending on the semiconductor laser dimensions are also included to investigate the effects of laser diode dimensions on the output pulse duration. Short duration optical pulses are generated by applying different electrical signals to the semiconductor laser with the help of this model. Among the parameters whose effects on the pulse duration are identified, gain compression, laser diode length, gain constant and iiiAuger recombination are found to be the most important ones. Comparison of the results with the previous works indicates that single-mode rate equations can not adequately model the generation of ultrashort pulses from laser diodes operating in multi-mode, especially for the lasers having large gain compression or small gain constant. Key words: semiconductor laser, gain switching, IV