Semiconductor Laser Stabilization By External Optical Feedback (original) (raw)
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Low-frequency fluctuations in semiconductor lasers with optical feedback are induced with noise
Physical Review E, 1998
We analyze the dynamics of a semiconductor laser with phase conjugate optical feedback, using numerical simulations based on rate equations for the complex amplitude of the electric field and the carrier density. From this analysis we observe the presence of low-frequency fluctuations which are similar to those observed in a semiconductor laser with conventional optical feedback. The similarities and differences between phase conjugate and conventional optical feedback are discussed, and a mechanism for the appearance of low-frequency fluctuations in a semiconductor laser with phase conjugate feedback is suggested.
Dynamical behavior of a semiconductor laser with filtered external optical feedback
IEEE Journal of Quantum Electronics, 1999
We report on a theoretical analysis of the dynamical performance of a semiconductor laser under the influence of delayed weak filtered external optical feedback. The filter widths considered range from 1 to 100 GHz. The analysis concentrates on the well-known low-frequency fluctuations (LFF's) regime, in which LFF's occur in the absence of filtering. As expected, filtering the feedback light stabilizes the system in general. LFF can already be suppressed for moderately broad filters (25-50 GHz). In that case, the system was found to operate on the maximum gain mode with a small amplitude limit cycle. We show how the filtering can, in principle, be used for targeting the laser on the maximum gain mode.
External noise in semiconductor lasers
SPIE Proceedings, 2004
In the present work we review recent results concerning stochastic phenomena in semiconductor lasers with optical feedback which operate in the low-frequency fluctuation (LFF) regime. Under these conditions the output intensity of the laser shows an irregular pulsated behavior in the form of sudden intensity dropouts. In the first two sections we show numerically the existence of stochastic and coherence resonance in the dropout appearance. These resonances are caused by the help of external colored noise introduced through the pumping current of the laser. In the third section we describe a recently reported new type of stochastic resonance, where a nonlinear system shows a resonance at a frequency not present neither at its internal time scales nor at any external perturbation. This phenomenon, known as ghost resonance, is reported both numerically and experimentally.
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.
Journal of Lightwave Technology, 1993
We review the theoretical framework for linewidth reduction in semiconductor lasers using optical feedback with dispersive loss. These results are then applied to lasers having both white and l/f frequency noise. Experimental confirmation of the dependence of frequency noise on feedback parameters is presented using optical feedback from an external cavity containing Cs vapor. We show that such feedback reduces the frequency noise spectrum uniformly within its operating bandwidth. We also show that where white noise is dominant, the linewidth is reduced by the same factor l/QZ as the frequency noise spectrum but when l/f noise dominates, the linewidth is reduced only by 1/Q.
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.
Noise characteristics of a single-mode laser diode subject to strong optical feedback
Journal of Lightwave Technology, 2002
An experimental study has been performed of the relative intensity noise (RIN) of a semiconductor laser in optical feedback regimes I to V. At low bias current, a low RIN is observed with low feedback ratio, the RIN increased in the coherence collapse regime (regime IV) and decreased in regime V. The RIN in regime V is lower than that of the solitary laser. For higher bias current, a higher feedback ratio is needed for the semiconductor laser to transit from regime IV to V. The measurements are found to be in good qualitative and quantitative agreement with theoretical predictions Index Terms-Laser diodes, noise, optical feedback.
Experimental and theoretical study of filtered optical feedback in a semiconductor laser
IEEE Journal of Quantum Electronics, 2000
We report on the systematical investigation of the steady-state regime and the dynamical behavior of a semiconductor laser subject to delayed filtered optical feedback. We study a Fabry-Perot (FP) interferometer type of filter placed in the external feedback loop of a diode laser. The effects of the filter on the locking of the diode laser frequency to the external cavity modes are described. We report and observe hysteresis, bistability, and multistability and show that all these are well described by a set of rate equations for the coupled laser and FP cavity system. We also present an experimental stability diagram that summarizes the dynamical behavior of the system.
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.