Fabien Rogister

Secure communication scheme using chaotic laser diodes subject to incoherent optical feedback and incoherent optical injection

We propose a secure communication scheme based on anticipating synchronization of two chaotic laser diodes, one subject to incoherent optical feedback and the other to incoherent optical injection. This scheme does not require fine tuning of the optical frequencies of both lasers as is the case for other schemes based on chaotic laser diodes subject to coherent optical feedback and injection. Our secure communication scheme is therefore attractive for experimental investigation.

Synchronization and communication with chaotic laser systems

Publisher Summary This chapter reviews the progress in the field of synchronization and communication with chaotic laser systems. The origin of chaotic dynamics in lasers is explained and illustrated, with accounts of experimental observations and with numerical computations on suitable models. It is shown how synchronization of chaotic laser systems leads to the possibility of communicating information in both digital and in analog form. The chapter presents an account of the latest advances in the field which employ semiconductor and fiber lasers, as well as gas and solid state laser systems. The possibility is discussed of developing secure communication systems, using chaos and nonlinear dynamics. Communication through the use of chaotic waveforms as carriers of information has been demonstrated by several groups, both in free space and through fiber channels. Information signals transmitted and received include digital and analog waveforms, and several different encoding and decoding schemes have been proposed and demonstrated in the chapter.

Experimental demonstration of suppression of low-frequency fluctuations and stabilization of an external-cavity laser diode

We demonstrate experimentally all-optical stabilization of a single-mode laser diode subject to external optical feedback operating in the low-frequency fluctuations (LFF) regime, by the technique of applying a second delayed optical feedback. We interpret our results as suppression of LFF through destruction of the antimodes responsible for the LFF crises and stabilization of the laser through creation of new maximum gain modes, in agreement with recent theoretical predictions.

Different regimes of low-frequency fluctuations in vertical-cavity surface-emitting lasers

A numerical study of vertical-cavity surface-emitting lasers with optical feedback demonstrates the existence of two different types of low-frequency fluctuations (LFFs). The competition of two equally dominant polarization modes characterizes one type of LFF, while the other type is characterized by power drops in a dominant polarization mode and power bursts in the orthogonal depressed mode. We characterize and compare these two types of LFFs on the basis of their polarization properties and their dependency on the laser parameters. We show furthermore that a transition is possible from one type of LFF to the other, depending on the values of the linear anisotropies of the vertical-cavity surface-emitting laser cavity.

Anticipating synchronization of two chaotic laser diodes by incoherent optical coupling and its application to secure communications

We demonstrate anticipating synchronization between two chaotic laser diodes respectively subjected to incoherent optical feedback and incoherent optical injection. We investigate the robustness of the synchronization with respect to small parameter mismatches and spontaneous emission noise. We show that the gain saturation strongly enhances the synchronization quality. We demonstrate that anticipating synchronization can be applied to cryptographic purposes. We check how difficult it is to intercept a message encoded by chaos shift keying without an adequate replica of the transmitter laser.

Suppression of low-frequency fluctuations and stabilization of a semiconductor laser subjected to optical feedback from a double cavity:?theoretical results

We demonstrate numerically that low-frequency fluctuations (LFFs) observed in a laser diode subjected to a first optical feedback with a short delay are suppressed by means of an adequate second optical feedback. The general idea of this technique is based on the observation that second feedback can suppress the antimodes that are responsible for the crises in the LFF regime. Furthermore, we observe that the second optical feedback can steer an unstable laser that is biased near threshold into a stable regime.

Symmetry breaking and high-frequency periodic oscillations in mutually coupled laser diodes

We investigate the dynamical behavior of two laser diodes coupled through mutual injection of their optical fields when placed face to face with a small separation between them. We report symmetry breaking in periodic solutions at low coupling rates. In addition, we demonstrate that at higher coupling rates both lasers exhibit very fast periodic oscillations. The system is of practical interest, since it constitutes a tunable all-optical source of microwave oscillations.

Asymmetric and delayed activation of side modes in multimode semiconductor lasers with optical feedback

We study the multimode dynamics of a semiconductor laser with optical feedback operating in the low-frequency fluctuation regime. A multimode extension of the Lang–Kobayashi (LK) model shows, in agreement with experimental observations, that the low-frequency power dropouts exhibited by the main modes are accompanied by sudden, asymmetric, activations of dormant longitudinal side modes. Furthermore, these activations are delayed with respect to the dropouts of the active modes. In order to satisfactorily reproduce both the asymmetric activation of side modes and their delay with respect to the dropouts, the generalized LK model has to include a parabolic gain profile, together with a frequency shift of the gain curve with carrier population.

Cryptographic scheme using chaotic laser diodes subject to incoherent optical feedback

We demonstrate numerically a secure communication scheme based on the synchronization of two chaotic laser diodes that are respectively subjected to incoherent optical feedback and incoherent optical injection. In this scheme, the optical fields emitted by the two lasers and the fields that are fed back and injected into these two lasers have orthogonal polarizations. Consequently, the external fields do not coherently interact with the lasing fields but only act on the population inversions. Synchronization of both lasers does not require fine tuning of their optical frequencies neither accurate control of the external cavity lengths contrary to the cryptographic systems based on conventional optical feedback. The message encoding/decoding is achieved by chaos shift keying.

Control of an external-cavity laser diode operating in the regular pulse package regime with a frequency shift of the optical feedback.

I demonstrate numerically that the regular pulse package regime observed in an external-cavity laser diode can be controlled by means of an adequate shift of the optical feedback frequency. This control leads to a stable pulsed behavior.