Vertical‐cavity surface‐emitting lasers with birefringence splitting above 250 GHz

Pusch, Tobias; Lindemann, Markus; Gerhardt, Nils C.; Hofmann, Martin R.; Michalzik, Rainer

doi:10.1049/el.2015.2149

Cited by 46 publications

(24 citation statements)

References 10 publications

(14 reference statements)

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“…PM supports the data transfer up to 240 Gbit/s, showing a remarkable improvement in digital operation over conventional VCSELs, consistent with the increase off 3dB over f 3dB . Improvements by further increasing ∆f mechanically [23,29], via photonic crystal [24] or strained quantum well-based VCSELs [18], potentially allowf 3dB > 1 THz. Unlike common approaches in spintronics and spin-lasers [3,30] which seek to increase the spin relaxation time (1/γ s ), we find that short spin relaxation times are desirable for PM.…”

mentioning

confidence: 99%

Ultrafast spin-lasers

Lindemann

Pusch

et al. 2019

Nature

172

134

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The appeal of lasers can be attributed to both their ubiquitous applications and their role as model systems for elucidating nonequilibrium and cooperative phenomena [1]. Introducing novel concepts in lasers thus has a potential for both applied and fundamental implications [2]. Here we experimentally demonstrate that the coupling between carrier spin and light polarization in common semiconductor lasers can enable room-temperature modulation frequencies above 200 GHz, exceeding by nearly an order of magnitude the best conventional semiconductor lasers. Surprisingly, this ultrafast operation relies on a short carrier spin relaxation time and a large anisotropy of the refractive index, both commonly viewed as detrimental in spintronics [3] and conventional lasers [4]. Our results overcome the key speed limitations of conventional directly modulated lasers and offer a prospect for the next generation of low-energy ultrafast optical communication.The global internet traffic will continue its dramatic increase in the near future [5]. Short-range and energy-efficient optical communication networks provide most of the communication bandwidth to secure the digital revolution. Key devices for high-speed optical interconnects, in particular in server farms, are current-driven intensity-modulated vertical-cavity surface-emitting lasers (VCSELs) [4]. Analogous to a driven damped harmonic oscillator, modulated lasers have a resonance frequency f R for the relaxation oscillations of the light intensity [6]. For higher frequencies the response decays and reaches half of its low-frequency value at f 3dB ≈ 1 + √ 2f R , which quantifies the usable frequency range [4]. In conventional VCSELs the modulation bandwidth is limited by the dynamics of the coupled carrier-photon system and parasitic as well as thermal effects. The current record is f 3dB = 34 GHz [7]. Common approaches to enhance the bandwidth rely on the expression f R = v g aS/τ p /(2π), where v g is the group velocity, a the differential gain, S the photon density, and τ p the * markus.lindemann@rub.de † nils.gerhardt@rub.de arXiv:1807.02820v1 [cond-mat.mes-hall]

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confidence: 99%

Ultrafast spin-lasers

Lindemann

Pusch

et al. 2019

Nature

172

134

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“…Often, it is assumed -also considering the typically large values of the spin-flip rate reported experimentally -that the adiabatic elimination of the spin-population difference could be a suitable approximation and would retain all essential non-linearities in the SFM model. Yet, in this work, we highlight that the impact of this adiabatic elimination on the polarization chaos and stability of the system steady-states is far too large to be neglected, even for large values of the spin-flip rate and, especially, for birefringence values in the order of tens of ns −1 and above [14], [15]. However, our analysis using the PCA and "False Neighbors" techniques confirm that there is potential for model order reduction, but it needs to be performed using methods that, unlike the adiabatic elimination of the spin-population, would preserve all key dynamical features of the model.…”

Section: Discussionmentioning

confidence: 95%

“…Email: mvirte@b-phot.org F. Ferranti is with the Microwave Department, Institut Mines-Télécom (IMT) Atlantique, CNRS UMR 6285 Lab-STICC, 29238 Brest CEDEX 3, France. Email: francesco.ferranti@imt-atlantique.fr that polarization dynamics could be embraced instead: thus leading to the tuning of polarization oscillations for high-speed spin-VCSELs [14], [15], polarization switching as optical memory mechanism [16]- [18] or random bit generation using polarization chaos [19]. The polarization features of VCSELs are accurately described using the so-called spin-flip model (SFM) [20], [21].…”

Section: Introductionmentioning

confidence: 99%

Chaos-Preserving Reduction of the Spin-Flip Model for VCSELs: Failure of the Adiabatic Elimination of the Spin-Population Difference

Virte¹,

Ferranti²

2019

IEEE J. Select. Topics Quantum Electron.

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When studying the dynamics of Vertical-Cavity Surface-Emitting Lasers, and their polarization properties, the spin-flip model appears to be the simplest model qualitatively reproducing all dynamical features that have been observed experimentally. Nonetheless, because of the fast time-scale of the spin-relaxation processes, the specific role and the importance of the spin-population difference -which is one of the specific feature of the spin-flip model -has been continuously questioned. In fact, the debate regarding the possible adiabatic elimination of the spin-population remains fully open.In this paper, our goal is to bring new light into this issue by demonstrating that this variable is essential to preserve the most complex dynamical features predicted by the spin-flip model, such as polarization chaos, and, therefore, needs to be conserved. To do so, we first perform a detailed analysis, focusing on the chaotic dynamics, to determine the minimal embedding dimension for the spin-flip model. As the latter confirms that a reduction of the model could be envisaged, we then consider the adiabatic elimination of the spin-population difference to highlight and explain its failure to reproduce essential dynamical features obtained in the original model.

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“…In a nutshell, a larger birefringence in the laser cavity could be expected to remove the two hurdles listed earlier, hence lead to better conditions to generate polarization chaos dynamics. In addition, it should be mentioned that this approach can be implemented in practice by stressing the laser mechanically which allows to tune the birefringence in the cavity to some extent 25,26 .…”

Section: Comparison With Experimental Observationsmentioning

confidence: 99%

Noise induced stabilization of chaotic free-running laser diode

Virte

2016

Chaos: An Interdisciplinary Journal of Nonlinear Science

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In this paper, we investigate theoretically the stabilization of a free-running vertical-cavity surface-emitting laser exhibiting polarization chaos dynamics. We report the existence of a boundary isolating the chaotic attractor on one side and a steady-state on the other side, and identify the unstable periodic orbit playing the role of separatrix. In addition, we highlight a small range of parameters where the chaotic attractor passes through this boundary, and therefore where chaos only appears as a transient behaviour. Then, including the effect of spontaneous emission noise in the laser, we demonstrate that, for realistic levels of noise, the system is systematically pushed over the separating solution. As a result, we show that the chaotic dynamics cannot be sustained unless the steady-state on the other side of the separatrix becomes unstable. Finally, we link the stability of this steady-state to a small value of the birefringence in the laser cavity and discuss the significance of this result on future experimental work.Semiconductor lasers -or laser diodes -are small, efficient and cheap laser devices and therefore are widely used for industrial applications. To generate a chaotic output however, since they typically behave as damped oscillators, an external perturbation such as optical feedback or modulation is required 1 .But recently, it has been shown that some specific semiconductor laser structures -namely Vertical-Cavity Surface-Emitting lasers (VCSELs) -could generate chaotic polarization fluctuations without the need for an external forcing due to a competition between two modes in the laser cavity 2 . The specific dynamics of VCSELs has been studied intensively for more than 20 years 3-11 , and polarization chaos has only been observed once, recently and only in nanostructured devices. Yet the theoretical framework reproducing accurately the observed dynamics does not take the specificities of the nanostructures into account 5,6 , which therefore raises the question: why has this dynamics never been observed in standard, commercial VCSELs before? Here we provide some elements of answer to this question. We theoretically highlight the existence of a separatrix between the chaotic dynamics and a steady-state, and demonstrate that the noise easily pushes the system over this boundary which therefore suppresses the chaotic dynamics. Moreover, we show that this mechanism appears for a large range of parameters, and in particular when the birefringence of the laser cavity is small. Finally, we discuss the relevance of this result by comparing available experimental data between chaotic and stable devices, and show that the chaos suppression mechanism described here is coherent with experimental reports.

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Vertical‐cavity surface‐emitting lasers with birefringence splitting above 250 GHz

Cited by 46 publications

References 10 publications

Ultrafast spin-lasers

Ultrafast spin-lasers

Chaos-Preserving Reduction of the Spin-Flip Model for VCSELs: Failure of the Adiabatic Elimination of the Spin-Population Difference

Noise induced stabilization of chaotic free-running laser diode

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