Nonlinear Photonics in semiconductor lasers: Solitonic microlasers and spin effects

Vertical-cavity surface-emitting lasers (VCSELs) show a very complex phenomenology of instabilities due to the presence of a large number of spatial, spectral and polarization degrees of freedom interacting with nonlinearities and disorder. Though the resulting limitations of their spatial and temporal coherence are usually considered to be a nuisance in applications, a proper understanding and design of the underlying self-organization processes can lead to new functionalities and devices. By frequency-selective feedback, emission can be funnelled into coherent microlasers which can be optically controlled, i.e. switched-on and off by external optical beams. These microlasers are a special form of a spatial soliton. We demonstrate frequency- and phase-locking of solitons defying the disorder. The locking phase vs. detuning follows an Adler scenario. Synchronization of laser solitons might provide a test bed for the interaction of complex networks of nonlinear oscillators. Spin dynamics can lead to ultra-fast self-oscillations based on polarization oscillations induced by birefringence, which are not subject to the usual limits for laser modulation given by the damping of intensity relaxation oscillations.