Yoann Noblet

Observation of laser vortex solitons in a self-focusing semiconductor laser

We report the observation of single and multiple vortex solitons in a self-focusing dissipative system, a broad-area vertical-cavity surface-emitting laser (VCSEL) with frequency-selective feedback by a volume Bragg grating. They are bistable and the transitions between different soliton structures are analysed. The observations qualitatively verify theoretical predictions based on simplified models for a semiconductor laser with frequency-selective feedback.

Disorder mapping in VCSELs using frequency-selective feedback

We report on a simple method with a high spectral and spatial resolution for mapping variations in the cavity resonance of a plano-planar broad-area laser based on frequency-selective feedback. The demonstration experiment uses a vertical-cavity surface-emitting-laser (VCSEL), in which growth induced inhomogeneities are of particular importance. It relies only on a standalone laser with a narrow-bandwidth passive filter avoiding the need for an expensive tunable laser or high-resolution spectrometer.

Frequency and phase locking of laser cavity solitons

Self-localized states or dissipative solitons have the freedom of translation in systems with a homogeneous background. When compared to cavity solitons in coherently driven nonlinear optical systems, laser cavity solitons have the additional freedom of the optical phase. We explore the consequences of this additional Goldstone mode and analyze experimentally and numerically frequency and phase locking of laser cavity solitons in a vertical-cavity surface-emitting laser with frequency-selective feedback. Due to growth-related variations of the cavity resonance, the translational symmetry is usually broken in real devices. Pinning to different defects means that separate laser cavity solitons have different frequencies and are mutually incoherent. If two solitons are close to each other, however, their interaction leads to synchronization due to phase and frequency locking with strong similarities to the Adler-scenario of coupled oscillators.

Analysis of spatial emission structures in vertical-cavity surface-emitting lasers with feedback from a volume Bragg grating

We investigate the spatial and spectral properties of broad-area vertical-cavity surface-emitting lasers with frequency-selective feedback by a volume Bragg grating. We demonstrate wavelength locking similar to the case of edge emitters but the spatial mode selection is different from the latter. On-axis spatial solitons obtained at threshold give way to off-axis extended lasing states beyond threshold. The investigations focus on a self-imaging external cavity. We analyze how deviations from the self-imaging condition affect the pattern formation and a certain robustness of the phenomena is demonstrated.

Observation of vortex soliton states in vertical-cavity surface-emitting lasers with feedback

We report on the formation of ring-shaped localized structures in addition to known spatial laser cavity solitons (LCS) in a broad-area vertical-cavity surface-emitting laser (VCSEL) with frequency-selective feedback, for which is providing the minimal model. As the injection current is increased, different scenarios are observed in which the LCS evolve from the fundamental soliton via multi-lobed and ring structures containing phase singularities to more complex patterns. We discuss their bistability and phase locking between a vortex and a fundamental soliton and between two vortices.

Locking of laser cavity solitons trapped by defects in VCSELs

Summary form only given. Laser cavity solitons (LCS) are transverse, nonlinear, self-localized and dissipative states that possess both translational and phase invariance. LCS interaction and synchronisation properties in broad-area semiconductor lasers have the potential for massive parallelism and the formation of complex arrays. Phase-locked bound states of solitons have been predicted in mode-locked lasers for the temporal case [1] and in lasers with saturable absorbers for the spatial case [2]. Corresponding phase-quadrature states have been observed in fibre lasers [1].Here we present a different kind of soliton locking. We demonstrate experimentally and theoretically Adlertype locking and synchronization of spatial LCS in a vertical-cavity surface-emitting laser (VCSEL) with an external volume Bragg grating (VBG) that provides frequency-selective feedback (see left panel of Fig.1) [3]. In particular we explain the role played by defects resulting from fluctuations during the epitaxial growth process. The experiment has been performed with a temperature tuned 981 nm VCSEL of 200 μm circular aperture and a VBG with a single reflection peak at 981.1 nm, and a peak reflectivity of 99% [3]. The external cavity for the frequency-selective feedback is arranged in a self-imaging configuration that maintains the high Fresnel number of the VCSEL cavity (see the left panel of Fig. 1). This potentially enables large parallelism of solitons and hence the prospect of synchronisation in large disordered networks.A piezo-electric transducer was used to minutely tilt the external cavitys end reflector (VBG) with respect to the optical axis. The differential change of the external cavity length for the two LCS leads to a differential change in feedback phase. In this way the detuning between two LCS can be tuned. During the scan, a region of frequency and phase locking appears, identified in the right panel of Fig. 1 by the region of high fringe visibility in the far field. This illustrates that locking - once achieved - is a robust phenomenon. We have theoretically and numerically investigated the interaction of pinned LCS upon the change of the difference in the depth of the trapping defects for both class-B semiconductor [4] and Ginzburg-Landau [5] models. In the locking region we recover an Adler scenario, where the fringe phase varies smoothly and quasilinearly with the detuning of the external cavity (see the red curve in the right panel of Fig. 1). The transitions to and from frequency and phase-locking are rather abrupt. Finally we discuss theoretical and experimental spectra in the locked and unlocked regions and the effect of the external cavity modes. Independent switching and erasure of locked and unlocked LCS is demonstrated.

Frequency and phase locking in a cavity soliton laser

The last few years have seen rapid progress in the creation of cavity solitons in broad-area semiconductor lasers. Such states represent small coherent microlasers which can be controlled by the operator thus making them interesting for optical information processing [1]. Here we investigate Laser Cavity Solitons (LCS) in a Vertical Cavity Surface Emitting Laser (VCSEL) with Frequency Selective Feedback (FSF). In our cavity soliton laser, the phase is not fixed and each LCS can have a different frequency due to disorder. Each LCS therefore has the freedom to choose its own frequency and phase. As such, it seems an interesting question to ask whether two or more of these self-localized states show frequency and phase locking behavior.

Analysis of pattern formation in vertical-cavity surface-emitting lasers with feedback of a volume Bragg grating

Broad-area VCSELs with frequency-selective feedback (FSF) from an external self-imaging cavity showed interesting effects like laser spatial solitons at threshold [1,2]. In this contribution we are investigating the influence of FSF on the spatially extended state of the VCSEL much further above threshold and contrast it to the behavior of an external cavity closed by a normal mirror. We also investigate deviations from the self-imaging condition. This meets interest of controlling the sign of diffraction, e.g. [3].