High-availability displacement sensing with multi-channel self mixing interferometry

Laser self-mixing is in principle a simple and robust general purpose interferometric method, with the additional expressivity which results from nonlinearity. However, it is rather sensitive to unwanted changes in target reflectivity, which often hinders applications with non-cooperative targets. Here we analyze experimentally a multi-channel sensor based on three independent self-mixing signals processed by a small neural network. We show that it provides high-availability motion sensing, robust not only to measurement noise but also to complete loss of signal in some channels. As a form of hybrid sensing based on nonlinear photonics and neural networks, it also opens perspectives for fully multimodal complex photonics sensing

Dissipative phase solitons in semiconductor lasers

We experimentally demonstrate the existence of non dispersive 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.Comment: 5 pages, 5 figure

Quantifying sudden changes in dynamical systems using symbolic networks

We characterise the evolution of a dynamical system by combining two well-known complex systems' tools, namely, symbolic ordinal analysis and networks. From the ordinal representation of a time-series we construct a network in which every node weights represents the probability of an ordinal patterns (OPs) to appear in the symbolic sequence and each edges weight represents the probability of transitions between two consecutive OPs. Several network-based diagnostics are then proposed to characterize the dynamics of different systems: logistic, tent and circle maps. We show that these diagnostics are able to capture changes produced in the dynamics as a control parameter is varied. We also apply our new measures to empirical data from semiconductor lasers and show that they are able to anticipate the polarization switchings, thus providing early warning signals of abrupt transitions.Comment: 18 pages, 9 figures, to appear in New Journal of Physic

Success rate analysis of the response of an excitable laser to periodic perturbations

We use statistical tools to characterize the response of an excitable system to periodic perturbations. The system is an optically injected semiconductor laser under pulsed perturbations of the phase of the injected field. We characterize the laser response by counting the number of pulses emitted by the laser, within a time interval, $\Delta$T , that starts when a perturbation is applied. The success rate, SR($\Delta$T), is then defined as the number of pulses emitted in the interval $\Delta$T , relative to the number of perturbations. The analysis of the variation of SR with $\Delta$T allows to separate a constant lag of technical origin and a frequency-dependent lag of physical and dynamical origin. Once the lag is accounted for, the success rate clearly captures locked and unlocked regimes and the transitions between them. We anticipate that the success rate will be a practical tool for analyzing the output of periodically forced systems, particularly when very regular oscillations need to be generated via small periodic perturbations.Comment: 7 pages, 7 figure

Measurement of the working parameters of an air-post vertical-cavity surface-emitting laser

We present a complete experimental evaluation of the effective parameters necessary to describe the dynamical behavior of an air-post vertical-cavity surface-emitting lasers, on the basis of theoretical equations which are also derived in this paper. The experimental investigation is composed of several steps, including power versus current measurement, noise spectrum analysis, linewidth evaluation. The complete set of parameters derived, in particular the linewidth-enhancement factor and the spontaneous emission factor, is particularly important for accurate comparisons of theoretical models on the laser dynamics with experiments

Efficient illumination for microsecond tracking microscopy.

The possibility to observe microsecond dynamics at the sub-micron scale, opened by recent technological advances in fast camera sensors, will affect many biophysical studies based on particle tracking in optical microscopy. A main limiting factor for further development of fast video microscopy remains the illumination of the sample, which must deliver sufficient light to the camera to allow microsecond exposure times. Here we systematically compare the main illumination systems employed in holographic tracking microscopy, and we show that a superluminescent diode and a modulated laser diode perform the best in terms of image quality and acquisition speed, respectively. In particular, we show that the simple and inexpensive laser illumination enables less than 1 μs camera exposure time at high magnification on a large field of view without coherence image artifacts, together with a good hologram quality that allows nm-tracking of microscopic beads to be performed. This comparison of sources can guide in choosing the most efficient illumination system with respect to the specific application

Localized vortices in semiconductor lasers

Beyond the chirality of light associated to polarization or spin, light beams can carry an additional orbital angular momentum due to the helicoidal structure of their phase front. This property, if combined with light localization could give rise to localized optical vortices, whose existence in nonlinear and dissipative optical systems is suggested by several theoretical studies. However, while several kinds of localized states have been experimentally found, no observation of localized vortices have been reported to date. We demonstrate the existence of bistable and addressable chiral localized structures in a semiconductor laser with saturable absorber. For a fixed set of parameters, we observe localized states with positive or negative topological charge, both coexisting with a fundamental "off" state. In contrast with phase defects and vortex solitons, the spatial structures described in this report are transversally localized and bistable due to the presence of dissipation. These properties, generically associated to localized structures, make localized vortices attractive for the realization of arrays of independant and controllable "doughnut shaped" beams which would dramatically enhance the efficiency of advanced optical nanoscopy techniques, especially in fast and compact sources such as semiconductor lasers

Stationary localized structures and pulsing structures in a cavity soliton laser

International audienc

Bistable and Addressable Localized Vortices in Semiconductor Lasers

International audienc