Chaos Synchronization In Semiconductor Lasers Research Articles

Chaos synchronization of semiconductor lasers over 1040-km fiber relay transmission with hybrid amplification

Optical chaos communication and key distribution have been extensively demonstrated with high-speed advantage but only within the metropolitan-area network range of which the transmission distance is restricted to around 300 km. For secure-transmission requirement of the backbone fiber link, the critical threshold is to realize long-reach chaos synchronization. Here, we propose and demonstrate a scheme of long-reach chaos synchronization using fiber relay transmission with hybrid amplification of an erbium-doped fiber amplifier (EDFA) and a distributed fiber Raman amplifier (DFRA). Experiments and simulations show that the hybrid amplification extends the chaos-fidelity transmission distance thanks to that the low-noise DFRA suppresses the amplified spontaneous emission noise and self-phase modulation. Optimizations of the hybrid-relay conditions are studied, including launching power, gain ratio of DFRA to EDFA, single-span fiber length, and number of fiber span. A 1040-km chaos synchronization with a synchronization coefficient beyond 0.90 is experimentally achieved, which underlies the backbone network-oriented optical chaos communication and key distribution.

多延时互耦合半导体激光器的实时混沌同步特性

Based on systems of semiconductor lasers with two mutual time-delayed couplings and three mutual time-delayed couplings,the influence of coupling delays and coupling strength to isochronal chaos synchronization was numerically studied.A thought that one coupling delay could be seen as feedback delays was presented in the system with two mutual time-delayed couplings.The condition and law for isochronal chaos synchronization was revealed in the system of semiconductor lasers with multiple mutual time-delayed couplings.The results show that the ratio 2 of two coupling delays is a basic condition to achieve isochronal chaos synchronization with high quality.Increasing coupling strength can improve the quality of isochronal chaos synchronization,and when the coupling strength is lower,the system with two mutual time-delayed couplings is much easier to achieve good isochronal chaos synchronization than system with three mutual time-delayed couplings.

Chaos synchronization in semiconductor lasers with polarization-rotated optical feedback

Chaotic oscillations of the transverse magnetic (TM) mode, which is not a common lasing mode, are excited by using polarization-rotated optical feedback from the transverse electric (TE) mode in a semiconductor laser. In our previous paper, we found that the dynamics were strongly dependent on their RF components under the condition of moderate optical feedback from the TE mode to the TM mode and that they were divided into three RF regions; low-pass filtered signals with a lower frequency than the laser relaxation oscillation frequency, intermediate RF components including the relaxation oscillation frequency, and high-pass filtered signals with a higher frequency higher than the relaxation oscillation frequency. Depending on the frequency bands, the laser outputs showed different correlations. In the present study, using such schemes, the polarization-rotated beam from a transmitter laser (i.e., the rotated TE-mode beam of a transmitter laser) is injected into a receiver laser. We experimentally observe chaos synchronization in accordance with the dynamics of RF components on the transmitter laser side. We also perform numerical calculations using a model and obtain good agreement between the theoretical and experimental results.

Numerical Analysis on Chaos Synchronization in Semiconductor Lasers Subject to a Common Drive Signal

We numerically observe chaos synchronization of two semiconductor lasers commonly driven by a chaotic semiconductor laser subject to optical feedback. We observe strongly correlated chaos synchronization between the two response lasers even when the correlation between the drive and response lasers is low. We show that the cross correlation between the two responses is larger than that between drive and responses over a wide parameter region.

Characteristics of Chaos Synchronization in Semiconductor Lasers Subject to Polarization- Rotated Optical Feedback

We numerically investigate the detailed characteristics of chaos synchronization in semiconductor lasers subject to polarization-rotated optical feedback. The emission of the dominant TE mode of a drive laser is rotated 90 deg and fed back to the laser with time delay. The polarization-rotated TE mode is also injected with time delay into the TM mode of a second laser. Two types of synchronization with different time-lags are found, as in the case for synchronization in semiconductor lasers with nonrotated optical feedback. However, a significant difference to the nonrotated optical feedback case is that neither of the two types of synchronization requires matching of optical carrier frequency between the two lasers.

Anticipating synchronization based on optical injection-locking in chaotic semiconductor lasers

Numerical studies for anticipating chaos synchronization in semiconductor lasers with optical feedback are presented. Anticipating chaos synchronization in a delay-differential system is believed to occur when all chaos parameters between the two systems are perfectly coincident with each other. However, we find new schemes of anticipating chaos synchronization when the parameters between the two systems have mismatches. Under these conditions, the time lag between the two laser outputs is equal to that of anticipating chaos synchronization, but the physical origin of the phenomenon comes from optical injection-locking or amplification in laser systems. We show the evidence of such chaotic synchronization using trajectories in the phase space of the phase difference and the carrier density in the laser oscillations.

Synchronization of chaos due to linear response in optically driven semiconductor lasers.

This paper presents physical aspects on chaos synchronization in semiconductor lasers (SLs) by studying synchronization from a fundamental standpoint of driven damped oscillators. We investigate the simple configuration, a chaotic master SL with optical feedback and a solitary slave SL. The point we emphasize is that the slave laser is regarded as a damped oscillator with relaxation oscillation. Linear stability analysis demonstrates that strong injection can enhance the damping of the slave SL. Consequently, the slave SL can have broad and nearly flat spectral characteristics in its driven response, which is sufficient for covering the broadband chaotic driving signal from the master SL. Numerical simulations verify that the slave SL subject to such strong injection synchronizes well with the chaotic driving signal. We consider that the synchronization phenomenon results from a quasilinear driven response of the slave SL with the remarkable spectral characteristics. Moreover, we discuss this type of chaos synchronization in comparison to anticipating-chaos synchronization occurring in our case from conventional complete synchronization theories, and clarify the different physical aspects of the chaos synchronization scheme. We also show that our analysis agrees well with the earlier experiments that could not have been explained by complete synchronization theory.