Cavity solitons (CSs) are self-localized spots formed in the transverse plane of a nonlinear cavity. They have been observed in various macroscopic systems, and predicted and observed in microscopic, semiconductor-based systems too. They are formed in a spatially extended, bistable, and modulationally unstable system driven by a coherent field (holding beam) and appear generally as bright spots sitting on a dark background. Their excitation is accomplished either spontaneously, by the noise present in the system, or by a local excitation. CSs can be independently addressed with a control beam and can be manipulated with the aid of phase or amplitude gradients of some control parameters. These properties make them interesting objects for all-optical information processing applications, for which they can be thought of as logical bit units for parallel information processing with reconfigurable capabilities. In that respect, semiconductor materials are particularly suited thanks to the time scales (1 ns or less) and spatial scales (～ 10 mm) that are involved. We will discuss on the observation of CSs in an optically-pumped, specially designed, semiconductor microcavity injected by a coherent beam in the amplifying regime [1]. CSs can be created spontaneously because of the noise present in the system or by a local perturbation. Initially, CSs where created and erased by a coherent local excitation in the holding beam profile with the need of a phase control between the writing and holding beams. However, CSs in semiconductors have an electric-field and a carrier component. Therefore, they could in principle be written or erased with an incoherent local excitation [2], whose wavelength is different from that of the pump and holding beams, and that locally adds carriers. In our experiment, CS are created by a local excitation pulse (60ps duration), by setting the system in the middle of the hysteresis cycle as shown on Fig. 1 (left). A roughly 200ns delay is associated with this process. Unexpectedly, incoherent switch-off was also observed, without any delay (Fig. 1 (right)). A clear explanation of these observations was not possible in the framework of existing theories taking into account the field and the carrier dynamics only. However we will show that including local detuning effects due to local heating can fully explain the observations. We will discuss the underlying physical mechanisms involved (cf Fig. 1), and present numerical simulations to assess our incoherent writing/erasure scheme. Other excitation processes that may reduce the switch-on delay will also be discussed.
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