Influence of amplitude-phase coupling on the dynamics of semiconductor lasers subject to optical feedback (original) (raw)
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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.
An improved analysis of semiconductor laser dynamics under strong optical feedback
IEEE Journal of Selected Topics in Quantum Electronics, 2003
We present an improved theoretical model to analyze dynamics and operation of semiconductor lasers under optical feedback (OFB). The model is applicable for arbitrary strength of OFB ranging from weak to very strong. The model has been applied to investigate the dynamics and operation of lasers over wide ranges of OFB and injection current. An improved set of modified rate equations of lasers operating under OFB were proposed. We introduced a theoretical model to determine the power emitted from both the laser back facet and external reflector. The results showed that the operation of semiconductor lasers is classified into continuous wave, chaotic, and pulsing operations, depending on the operating conditions. The light versus current characteristics were examined in the operating regions of the classified operations. Under strong OFB, we predicted for the first time pulsing operation of lasers at injection currents well above the threshold. We observed the pulsing operation in experiments in good correspondence with the simulated results.
Physical Review A, 1998
We present a systematic investigation of the dynamical behavior of semiconductor lasers subject to external optical feedback dependent on the injection current and the optical feedback strength. We identify the regimes of low-frequency fluctuations ͑LFFs͒, fully developed coherence collapse, and a large regime of the coexistence of LFFs and stable emission on single high-gain external-cavity mode extending over more than one order of magnitude of optical feedback strengths. Thus, we provide experimental evidence for one major prediction of the theoretical model based on the Lang-Kobayashi equations, which proposes a deterministic mechanism underlying the LFFs.
Effect of phase-conjugate feedback on semiconductor laser dynamics
Optics Letters, 1991
The effect of phase-conjugate feedback on the dynamic response of semiconductor lasers is studied by using a rate-equation approach. The steady state exists only for certain well-defined values of the phase of the intracavity optical field. Depending on the amount of phase-conjugate feedback, the steady state becomes unstable through two independent instabilities, referred to as fold and Hopf instabilities. The fold instability is due solely to the phase-conjugate nature of the feedback and does not occur in the case of normal feedback. In the instability region, the laser output is found to become chaotic by following a period-doubling or quasi-periodic route to chaos, depending on the amount of feedback.
Optical spectra of a semiconductor laser with incoherent optical feedback
IEEE Journal of Quantum Electronics, 1990
We experimentaly investigate the spectrum of a semiconductor laser with incoherent feedback from a distant mirror, i.e., the external round-trip time exceeds the coherence time of the laser. As the amount of feedback increases, the optical spectrum evolves from a central line with enhanced isolated satellite peaks caused by the relaxation oscillation to a very broad ( -20 GHz) line, where the relaxation oscillation gives rise to shoulders. Moreover, there is an asymmetry for frequencies above or below the central frequency. This drastic change of the spectrum is also found from a recent theoretical description of a semiconductor laser in the coherence collapsed state. The amount of feedback and the damping rate of the relaxation oscillation are obtained from a fit of the theory to the observed time-autocorrelation function. This analysis reveals that, owing to incoherent feedback, the damping rate of the relaxation oscillation behaves as an effective damping rate that depends almost linearly on the feedback rate.
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 .
Journal of the Optical Society of America B, 2005
We show that a laser diode that is subject to optical feedback from a short external cavity (EC) may exhibit types of regular pulse packages (RPPs) that differ in their underlying intensity behavior. As we modify the EC's length, the laser injection current, or both, the RPP dynamics exhibit either a monotonically decaying intensity from pulse to pulse or a first increasing and then decreasing pulse intensity. The mechanism underlying the transition from one RPP type to the other type is found to be related to the carrier excursion in the system's trajectory among EC modes. Furthermore, we show that the change of the intensity behavior inside the RPP anticipates the intensity dynamics that are typical for a long-EC regime, i.e., low-frequency fluctuations (LFFs). We then unveil a transition between the short and the long EC dynamic regime. The link between these dynamic states is further confirmed by analysis of the dependency of the period of RPP dynamics on the injection current, which is found to be similar to that of the mean time between irregular bursts of pulses in the LFF dynamics.
Filtered Optical Feedback Induced Dynamics in Semiconductor Lasers
2003
A diode laser with optical feedback is a paradigm for studying nonlinear dynamics in delayed feedback systems. Filtered optical feedback (FOF), during which the spectral content of feedback light is altered by a filter, provides a mechanism for controlling the dynamical response of a laser. A filter, due to its nonlinear response function, introduces a controllable nonlinearity in the feedback system, and its influence on the laser dynamics can be manipulated via the filter?s bandwidth, and its detuning from the laser frequency. FOF offers several advantages over conventional optical feedback (COF), which we will enumerate. Most importantly, we demonstrate in this paper that one can exploit the interplay between the nonlinear response of the filter, and the a-parameter of the laser, to induce novel dynamics in the frequency of light from the laser. The origin of frequency dynamics can be qualitatively motivated by recognizing two facts; firstly, a filter alters the amplitude of the ...
Experimental and Theoretical Study of Semiconductor Laser Dynamics Due to Filtered Optical Feedback
IEEE Journal of Selected Topics in Quantum Electronics, 2004
We report experimental results on the nonlinear dynamical response of a semiconductor laser subjected to time-delayed ( 5 ns), frequency selective, optical feedback from a Fabry-Pérot interferometer type of filter. Three regimes of interest, based on the relative value of the filter bandwidth with respect to the relevant laser parameters (relaxation oscillation frequency and external cavity mode spacing), are identified, viz. a wide filter case, an intermediate filter width case, and a narrow filter case. The dynamical response of the laser is shown to be quite different in each of these regimes. The principal results are 1) the laser's linewidth enhancement factor, coupled with the nonlinear response of the filter, can be exploited to induce nonlinear dynamics in the instantaneous optical frequency of the laser light on a time scale related to the time-delay of the feedback, 2) a mode mismatch effect which arises from a detuning between the filter center frequency and the nearest external cavity mode and manifests itself in a reduction of the maximum light available for feedback, and 3) a reduction in, or even disappearance of, relaxation oscillations in the laser dynamics when a filter of appropriate width is chosen. More generally, it is observed that certain dynamics that occur due to unfiltered optical feedback may be suppressed when the feedback light is spectrally filtered.