Nonlinear interaction between a coherent electric field and a semiconductor medium inside a high Fresnel number cavity may give rise to the formation of cavity solitons. It is theoretically predicted that the position of these structures, mutually independent and bistable, can be controlled by gradients in the injection beam. Using a liquid crystal light valve to spatially modulate the phase of a coherent beam injected into a broad area vertical cavity semiconductor laser, the authors create reconfigurable arrays of cavity solitons. Fast time scales associated with semiconductor lasers and plasticity of localized structures suggest their potential for optical data processing.

We experimentally demonstrate the existence of nondispersive solitary waves associated with a $2\pi$ phase rotation in a strongly multimode ring semiconductor laser with coherent forcing. Similarly to Bloch domain walls, such structures host a chiral charge. The numerical simulations based on a set of effective Maxwell-Bloch equations support the experimental evidence that only one sign of chiral charge is stable, which strongly affects the motion of the phase solitons. Furthermore, the reduction of the model to a modified Ginzburg-Landau equation with forcing demonstrates the generality of these phenomena and exposes the impact of the lack of parity symmetry in propagative optical systems.

We report on an experimental study of photon thermalization and condensation in a semiconductor microresonator in the weak-coupling regime. We measure the dispersion relation of light and the photon mass in a single-wavelength, broad-area resonator. The observed luminescence spectrum is compatible with a room-temperature, thermal-equilibrium distribution. A phase transition, identified by a saturation of the population at high energies and a superlinear increase of the occupation at low energy, takes place when the phase-space density is of order unity. We explain our observations by Bose-Einstein condensation of photons in equilibrium with a particle reservoir and discuss the relation with laser emission.

Semiconductor lasers with coherent forcing are expected to behave similarly to simple neuron models in response to external perturbations, as long as the physics describing them can be approximated by that of an overdamped pendulum with fluid torque. Beyond the validity range of this approximation, more complex features can be expected. We perform experiments and numerical simulations which show that the system can display resonator and integrator features depending on parameters and that multiple pulses can be emitted in response to larger perturbations.

A cavity soliton laser is a device able to generate single-peak localized structures, also called cavity solitons, without the injection of an external coherent beam. We realized experimentally a cavity soliton laser by mutually coupling in face to face configuration two broad-area vertical cavity surface emitting lasers, one set to work as amplifier while the second, biased below transparency, plays the role of a saturable absorber. We explore the parameter space, showing the robustness of cavity solitons in this system, and we analyze their switching process. We also report on structures pulsing at the roundtrip time of the compound cavity defined by the two devices. Despite these structures look very similar to cavity solitons in terms of the time-averaged intensity profile, they cannot be interpreted as pulsing cavity solitons since there is no bistability associated with them.