Stéphane Barland

Cavity solitons as pixels in semiconductor microcavities

Cavity solitons are localized intensity peaks that can form in a homogeneous background of radiation. They are generated by shining laser pulses into optical cavities that contain a nonlinear medium driven by a coherent field (holding beam). The ability to switch cavity solitons on and off and to control their location and motion by applying laser pulses makes them interesting as potential ‘pixels’ for reconfigurable arrays or all-optical processing units. Theoretical work on cavity solitons has stimulated a variety of experiments in macroscopic cavities and in systems with optical feedback. But for practical devices, it is desirable to generate cavity solitons in semiconductor structures, which would allow fast response and miniaturization. The existence of cavity solitons in semiconductor microcavities has been predicted theoretically, and precursors of cavity solitons have been observed, but clear experimental realization has been hindered by boundary-dependence of the resulting optical patterns—cavity solitons should be self-confined. Here we demonstrate the generation of cavity solitons in vertical cavity semiconductor microresonators that are electrically pumped above transparency but slightly below lasing threshold. We show that the generated optical spots can be written, erased and manipulated as objects independent of each other and of the boundary. Numerical simulations allow for a clearer interpretation of experimental results.

Polarization dynamics in vertical-cavity surface-emitting lasers with optical feedback: experiment and model

Experiments and their interpretation on polarization dynamics and polarization switching in vertical-cavity surface-emitting lasers operated in the fundamental transverse mode regime are reviewed. Important observations are switching events to a mode with the lower unsaturated gain and the existence of elliptically polarized dynamical transition states after the destabilization of the low-frequency polarization mode. The observations demonstrate the need to consider explicitly the phase properties of the optical field as well as nonlinear effects affecting polarization selection above threshold. Good qualitative agreement is found with a model which takes into account the spin degrees of freedom of the light field as well as of the carriers (`spin-flip model), if the spin-flip rate is taken to be some tens of

Topological solitons as addressable phase bits in a driven laser

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Low-frequency fluctuations in vertical cavity lasers : Experiments versus Lang-Kobayashi dynamics

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Spatial mode structure of bottom-emitting broad-area vertical-cavity surface-emitting lasers

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Spatial structure of broad-area vertical-cavity regenerative amplifiers.

. This constitutes a strong -- though indirect -- indication that spin dependent processes are important in polarization selection in the devices investigated.

Regenerative memory in time-delayed neuromorphic photonic resonators

Optical localized states are usually defined as self-localized bistable packets of light, which exist as independently controllable optical intensity pulses either in the longitudinal or transverse dimension of nonlinear optical systems. Here we demonstrate experimentally and analytically the existence of longitudinal localized states that exist fundamentally in the phase of laser light. These robust and versatile phase bits can be individually nucleated and canceled in an injection-locked semiconductor laser operated in a neuron-like excitable regime and submitted to delayed feedback. The demonstration of their control opens the way to their use as phase information units in next-generation coherent communication systems. We analyse our observations in terms of a generic model, which confirms the topological nature of the phase bits and discloses their formal but profound analogy with Sine-Gordon solitons.

Single-mode operation and transverse-mode control in VCSELs induced by frequency-selective feedback

The limits of applicability of the Lang-Kobayashi (LK) model for a semiconductor laser with optical feedback are analyzed. The model equations, equipped with realistic values of the parameters, are investigated below the solitary laser threshold where low-frequency fluctuations (LFFs) are usually observed. The numerical findings are compared with experimental data obtained for the selected polarization mode from a vertical cavity surface emitting laser (VCSEL) subject to polarization selective external feedback. The comparison reveals the bounds within which the dynamics of the LK model can be considered as realistic. In particular, it clearly demonstrates that the deterministic LK model, for realistic values of the linewidth enhancement factor {alpha}, reproduces the LFFs only as a transient dynamics towards one of the stationary modes with maximal gain. A reasonable reproduction of real data from VCSELs can be obtained only by considering the noisy LK or alternatively deterministic LK model for extremely high {alpha} values.

Dissipative Phase Solitons in Semiconductor Lasers.

The spatial mode structure of circular broad-area bottom-emitting vertical-cavity surface-emitting lasers is investigated close to threshold. The devices display very high-order flower-like Laguerre modes as well as structures with a Cartesian symmetry in spite of the original O(2) symmetry. In some cases the latter resemble tilted waves more than Hermite-Gaussian modes. Spatial structures appear for both sides of the detuning between the gain peak and the cavity resonance. The results indicate the necessity to refine the theoretical models to include realistic boundary conditions and inhomogeneities.

Periodic and chaotic solitons in a semiconductor laser with saturable absorber.

We investigate the spatial structure of broad-area vertical-cavity regenerative amplifiers injected with a homogeneous beam. The emerging patterns have a predominantly sixfold rotational symmetry, verifying the recent prediction of formation of hexagons. The length scale is controllable by means of detuning and follows the prediction for tilted waves.