Localized pulses in passively mode-locked semiconductor lasers

In this contribution we describe recent results on the generation and control of temporal localized structures in a passively mode-locked Vertical-Cavity Surface-Emitting Laser mounted in an external cavity closed by a resonant saturable absorber mirror. When the cavity roundtrip is much larger than the medium timescales, this system exhibits a temporal aspect-ratio large enough to host pulses which can be individually addressed. These localized pulses have been proposed as information bits and the possibility of their manipulation opens interesting perspectives for information processing. We will show that a modulation of the pumping current leads to control the position and the speed of the localized pulses within the cavity. In addition to pin the pulses at well-defined positions, which enables clocking the bit flow, the pulses can be driven to collide one against the other, thus unveiling the purely repulsive mutual interaction.