Asymmetric and delayed activation of side modes in multimode semiconductor lasers with optical feedback (original) (raw)
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Dynamics of power distribution in multimode semiconductor lasers with optical feedback
2002
ABSTRACT Semiconductor lasers with optical feedback are prone to exhibit unstable behavior. When working near threshold with moderate to low optical feedback, intensity dropouts are observed. These intensity drops, also called low-frequency fluctuations, occur both in single-mode and multimode semiconductor lasers. In this paper, the dynamics of the power distribution between the longitudinal modes of a multimode semiconductor laser is experimentally and numerically analyzed in the low-frequency fluctuation regime. It is observed that power dropouts of the total intensity, corresponding to drops in the dominant modes of the laser, are invariably accompanied by sudden activations of several longitudinal side modes. These activations are seen not to be simultaneous to the dropouts of the main modes, but to occur after them. The phenomenon is statistically analyzed in a systematic way, and the corresponding delay is estimated, leading to the conclusion that the side mode activation is a consequence of the dropouts of the dominant modes. A multimode extension of the Lang-Kobayashi equations is used to model the experimental setup. Numerical simulations also exhibit a time delay between the side-mode activation and the power dropout of the total intensity.
Physical Review E, 1999
Semiconductor lasers with optical feedback present a regime in which power dropouts are observed. Although this regime has been extensively studied, there is no agreement about whether the dropouts are deterministically or stochastically generated. In this paper we will study the statistics of time intervals between dropouts assuming noise-driven simple excitable models. We explain the appearance of characteristic times in the first return maps. ͓S1063-651X͑99͒00408-0͔
Statistics of power-dropout events in semiconductor lasers with time-delayed optical feedback
Physical Review A, 1997
We measure experimentally the statistical distribution of time intervals between power-dropout events occurring in a semiconductor laser with time-delayed optical feedback operating in the low-frequency fluctuation regime. Near the laser threshold, the time-interval probability distribution displays a low-probability region, or dead zone, for short times, followed by a slow rise, and an exponential decay for long times. At higher injection currents, the distributions develop considerable structure. We compare our results to the predictions of approximate analytic models of the laser dynamics and find that no single model accurately captures the details of the observed distributions, indicating that our physical understanding of the long-term dynamics of the laser in this regime is less than complete. ͓S1050-2947͑97͒50711-6͔
Low frequency fluctuations and multimode operation of a semiconductor laser with optical feedback
Optics Communications, 1998
We experimentally investigate low frequency fluctuations LFF in a Fabry-Perot semiconductor laser with optical feedback from an external mirror. During LFF, the time resolved optical spectrum shows that many longitudinal modes of the solitary laser enter into the transients. After each LFF event, the excited solitary-laser modes recover similarly. However, the recovery for the power in each mode is much slower than the recovery of the total power. The intermode exchange of energy during the recovery indicates that a single-longitudinal mode description of such LFF behavior will not capture important underlying dynamics. The relevance of multimode dynamics is confirmed in a feedback experiment where the external mirror is substituted by a diffraction grating. q 1998 Elsevier Science B.V.
Temporal Dynamics of Semiconductor Lasers with Optical Feedback
Physical Review Letters, 1998
We measure the temporal evolution of the intensity of an edge emitting semiconductor laser with delayed optical feedback for time spans ranging from 4.5 to 65 ns with a time resolution from 16 to 230 ps, respectively. Spectrally resolved streak camera measurements show that the fast pulsing of the total intensity is a consequence of the time delay and multimode operation of the laser. We experimentally observe that the instabilities at low frequency are generated by the interaction among different modes of the laser. [S0031-9007(98)08077-6] PACS numbers: 05.45. + b, 05.40. + j, 42.60.Mi Nonlinear systems with delayed feedback are of interest because they can be widely found in economy, biology, chemistry, and physics [1]. These systems are in principle infinite dimensional, and from this point of view, it is difficult to classify them a priori as deterministic dynamical systems because the existence and uniqueness of a solution have to be demonstrated for each particular model . It is also difficult to separate the role of noise from determinism, because complex solutions display a Gaussian-Markovian behavior as if they were solutions of a Langevin equation , thus nonconventional measurement techniques are required .
Applied Physics B, 2018
Comprehensive theoretical investigation of the influence of external optical feedback on the dynamics of semiconductor lasers are introduced. The analyses are based on numerical simulation of the multimode rate equations superposed by Langevin noise sources that are generated in such a way as to keep the correlation of the modal photon number with the injected electron number. The gain saturation effect which causes mode-competition phenomena among longitudinal modes are considered in our multimode rate equation model. The dynamics of modes and the characteristics of the output spectrum are investigated for strong external optical feedback strength. Numerically simulated results show that the mode-competition phenomena induce quasi-periodic hopping among several longitudinal modes which reveals multimode-like output spectra in lasers. This mode-hopping phenomena is described in terms of asymmetric gain saturation effect.
This paper introduces a theoretical study of longitudinal mode competition in semiconductor lasers subject to optical feedback. The study is based on a model of time-delay multimode rate equations taking into account both symmetric and asymmetric suppressions of modal gain. The model is numerically solved and applied to the case of a short-external cavity. Mode competition is characterized along the feedback-induced period-doubling route to chaos as well as under chaotic dynamics. Contributions of symmetric and asymmetric gain suppressions to both mode dynamics and modal operation under OFB are clarified. The results show that under chaotic dynamics, mode competition induces multimode hopping giving rise to asymmetric multimode output spectra. In regimes of continuous-wave operation, mode competition supports single-mode oscillation, and the side-mode suppression ratio improves with the increase of feedback. In the regime of strong feedback, the lasing mode moves to either long-or short-wavelength side in a seemingly random fashion, which is strongly related to asymmetric gain suppression.
Stabilization of feedback-induced instabilities in semiconductor lasers
Journal of Optics B: Quantum and …, 2000
We present extensive studies on feedback-induced instabilities in semiconductor lasers (SLs) subject to delayed optical feedback. We demonstrate that a sufficient reduction of the linewidth enhancement factor α changes the dynamical structure of the system such that permanent emission in a stable emission state is achieved. This behaviour can be well understood on the basis of the Lang-Kobayashi rate equation model. We give first experimental evidence for its major theoretical predictions concerning the stable emission state and investigate the robustness of this stable state against external perturbations. We demonstrate that noise-induced escape from the basin of attraction of the stable state shows similarities to the classical problem of thermally induced escape from a potential well. Thus, we have developed and realized experimentally an efficient concept to avoid and stabilize feedback-induced instabilities in SLs.