Sylvain Barbay

Excitability in a semiconductor laser with saturable absorber

We show that a monolithic and compact vertical cavity laser with intracavity saturable absorber can emit short excitable pulses. These calibrated optical pulses can be excited as a response to an input perturbation whose amplitude is above a certain threshold. Subnanosecond excitable response is promising for applications to novel all-optical devices for information processing or logical gates.

Optical Bistability in a GaAs-Based Polariton Diode

We report on a new type of optical nonlinearity in a polariton p-i-n microcavity. Abrupt switching between the strong and weak coupling regime is induced by controlling the electric field within the cavity. As a consequence, bistable cycles are observed for low optical powers (2-3 orders of magnitude less than for Kerr induced bistability). Signatures of switching fronts propagating through the whole 300 x 300 microm2 mesa surface are evidenced.

Incoherent and coherent writing and erasure of cavity solitons in an optically pumped semiconductor amplifier

Cavity solitons in semiconductor amplifiers were, from the beginning of their study and observation, obtained either spontaneously or in a controlled manner by local coherent excitation. We describe two experiments that demonstrate coherent and, we believe for the first time, incoherent writing and erasure of cavity solitons in an optically pumped vertical-cavity semiconductor amplifier by short optical pulses.

Frequency response of polarization switching in vertical-cavity surface-emitting lasers

We present an experimental study of the current-driven polarization modulation properties of VCSELs. In some VCSELs, abrupt polarization switching (PS) between two polarization modes is observed at a particular value of the pump current. We investigate the dynamics and the associated dominating time scales of PS as these features are strongly linked with the underlying physical mechanism causing the PS. To this end, we measure both for gain- and index-guided VCSELs the critical modulation amplitude necessary to steadily force PS back and forth across the PS point as a function of the modulation frequency. This yields the current-driven polarization modulation frequency response, which we compare with the thermal frequency response of the studied devices. The dynamic behavior turns out to be strikingly different for the different VCSEL types. Thermal effects only play a minor role in the PS in our index-guided VCSELs, while they really seem to lie at the origin of PS in the gain-guided VCSELs. By implementing this in a rate-equation based theoretical model, we are able to explain the peculiarities of the measured response curves and to reproduce the experimental findings.

Spatiotemporal Chaos Induces Extreme Events in an Extended Microcavity Laser

Extreme events such as rogue waves in optics and fluids are often associated with the merging dynamics of coherent structures. We present experimental and numerical results on the physics of extreme event appearance in a spatially extended semiconductor microcavity laser with an intracavity saturable absorber. This system can display deterministic irregular dynamics only, thanks to spatial coupling through diffraction of light. We have identified parameter regions where extreme events are encountered and established the origin of this dynamics in the emergence of deterministic spatiotemporal chaos, through the correspondence between the proportion of extreme events and the dimension of the strange attractor.

Frequency response of current-driven polarization modulation in vertical-cavity surface-emitting lasers

We present an experimental study of the current-driven polarization modulation properties of vertical-cavity surface-emitting Lasers (VCSELs). Some VCSELs exhibit a high-contrast polarization flip for a particular value of pump current. By modulating the current around this value we measure the critical modulation amplitude necessary to force current-driven polarization switching as a function of the modulation frequency. We thus obtain the polarization modulation frequency response, which shows the same cut-off frequency as the thermal frequency response. This indicates the necessity to incorporate a temperature-dependent variable in realistic models that describe the polarization behavior of these VCSELs.

Cavity Solitons in VCSEL Devices

We review advances on the experimental study of cavity solitons in VCSELs in the past decade. We emphasize on the design and fabrication of electrically or optically pumped broad-area VCSELs used for CSs formation and review different experimental configurations. Potential applications of CSs in the field of photonics are discussed, in particular the use of CSs for all-optical processing of information and for VCSELs characterization. Prospects on self-localization studies based on vertical cavity devices involving new physical mechanisms are also given.

Transient chirp in high-speed photonic-crystal quantum-dot lasers with controlled spontaneous emission

We report on a series of experiments on the dynamics of spontaneous emission controlled nanolasers. The laser cavity is a photonic-crystal slab cavity, embedding self-assembled quantum dots as gain material. The implementation of cavity electrodynamics effects increases the large signal modulation bandwidth significantly, with measured modulation speeds of the order of 10 GHz while keeping an extinction ratio of 19 dB. A linear transient wavelength shift is reported, corresponding to a chirp of less than 100 pm for a 35 ps laser pulse. We observe that the chirp characteristics are independent of the repetition rate of the laser up to 10 GHz.

Temporal summation in a neuromimetic micropillar laser

Neuromimetic systems are systems mimicking the functionalities or architecture of biological neurons and may present an alternative path for efficient computing and information processing. We demonstrate here experimentally temporal summation in a neuromimetic micropillar laser with an integrated saturable absorber. Temporal summation is the property of neurons to integrate delayed input stimuli and to respond by an all-or-none kind of response if the inputs arrive in a sufficiently small time window. Our system alone may act as a fast optical coincidence detector and paves the way to fast photonic spike-processing networks.

Optical patterns and cavity solitons in quantum-dot microresonators

We study optical transverse instabilities in quantum-dot (QD) microresonators. We develop a model for the QD susceptibility taking into account the inhomogeneous broadening of the dot emission. A linear stability analysis and numerical integration of the resulting equations are performed. Special attention is paid to the formation of such structures as optical patterns and cavity solitons, which could play an important role in the field of optical information processing. Implications for actual QD materials are discussed in view of applications.