Picosecond dynamic processes of semiconductor lasers allow the generation of short optical pulses which find applications in a rich variety of relevant technological fields. In this book, a simple analysis of the semiconductor laser dynamics, based on the well known rate equation model, is reviewed. A particular device is considered for modeling and experiments: the 1550 nm Vertical Cavity Surface Emitting Laser (VCSEL). Recent original results obtained with these devices are presented. Attention is given to the characterization of the devices and to the analysis of the pulses generated with the Gain Switching technique. Pulse duration, amplitude and jitter are studied as a function of the Gain Switching parameters. The effect of external optical injection on the pulse jitter reduction is presented and an Optical Code Division Multiple Access encoder, based on the obtained pulse train, is described. Additionally, a novel technique for the measurement of the pulse frequency chirp is presented and applied to the calculation of the linewidth enhancement factor of the laser.