Mutually Coupled Semiconductor Lasers Research Articles

Design of parallel reservoir computing by mutually-coupled semiconductor lasers with optoelectronic feedback

Via implementing parallel tasks including Santa-Fe time series prediction and nonlinear channel equalization, we studied the characteristics of reservoir computing (RC) using two mutually-coupled semiconductor lasers (MC-SLs) with optoelectronic feedback. The influence of system parameters (injection current, coupling strength, scaling factor and coupling time-delays) on RC performance have been investigated in detail. Results show that, the optimized performance is always achieved around the edge of bifurcation points; positive feedback is more preferred when the scaling factor exceeds a certain level; under optimized parameters, both of lower normalized mean squared error (NMSE) and symbol error rate (SER) can be achieved to perform parallel tasks, due to the richer dynamics and states of virtual nodes. The effect of system parameters on RC performance was also discussed. Our study would be helpful for the design and optimization of proposed parallel RC with optoelectronic feedback.

Random-injection-based two-channel chaos with enhanced bandwidth and suppressed time-delay signature by mutually coupled lasers: Proposal and numerical analysis* *Project supported by the Sichuan Science and Technology Program, China (Grant No. 2019YJ0530), the Scientific Research Fund of Sichuan Provincial Education Department, China (Grant No. 18ZA0401), the Innovative Training Program for College Student of Sichuan Normal University, China (Grant No. S20191063609), and

Simultaneous bandwidth (BW) enhancement and time-delay signature (TDS) suppression of chaotic lasing over a wide range of parameters by mutually coupled semiconductor lasers (MCSLs) with random optical injection are proposed and numerically investigated. The influences of system parameters on TDS suppression (characterized by autocorrelation function (ACF) and permutation entropy (PE) around characteristic time) and chaos BW are investigated. The results show that, with the increasing bias current, the ranges of parameters (detuning and injection strength) for the larger BW (> 20 GHz) are broadened considerably, while the parameter range for optimized TDS (< 0.1) is not shrunk obviously. Under optimized parameters, the system can simultaneously achieve two chaos outputs with enhanced BW (> 20 GHz) and perfect TDS suppression. In addition, the system can generate two-channel high-speed truly physical random number sequences at 200 Gbits/s for each channel.

Time-delay signature concealment of chaos and ultrafast decision making in mutually coupled semiconductor lasers with a phase-modulated Sagnac loop.

We propose and experimentally demonstrate the generation of dual-channels chaos with time delay signature (TDS) concealment by introducing a phase-modulated Sagnac loop in mutually coupled semiconductor lasers (MCSL). Furthermore, we demonstrate the utilization of the dual-channels chaos to solve multi-armed bandit (MAB) problem in reinforcement learning. The experimental results agree well with the numerical simulations. For the purpose of comparison, the MCSL with a conventional Sagnac loop is also considered. It is found that the TDS of dual-channels chaotic signals can be better concealed in our proposed system. Besides, the proposed system allows for a better decision making performance in MAB problem. Moreover, compared with the one-channel chaotic system, the proposed dual-channels chaotic system achieves ultrafast decision making in parallel, and thus, is highly valuable for further improving the security of communication systems and the performance of photonic intelligence.

Cluster Synchronization of Coupled Semiconductor Lasers Network With Complex Topology

The cluster synchronization of mutually-coupled semiconductor lasers (SLs) network with complex topology is theoretically and numerically investigated, in which stable zero-lag synchronization could be achieved between different SLs within same cluster. It is shown that the symmetry of SLs network topology is an underlying mechanism for the formation of SLs clusters. Different SLs clusters can exhibit different local dynamics and, most importantly, synchronized SLs clusters could coexist with unsynchronized ones. We also discussed the influence of the significant parameters of SLs on the stability of cluster synchronization. The numerical results show that two key internal parameters of SLs, the linewidth-enhancement factor and gain saturation coefficient, play important roles on the SLs network dynamics. It is also shown that, from the point view of symmetry, the self-feedback strength of SLs can play a particularly important role on the formation of SLs cluster. Moreover, the existence of symmetry-induced cluster synchronization is verified in different types of SLs networks topologies (random network and Nepal power grid network), indicating the universality of proposed results. Our results suggest a new insight into the research of synchronized dynamics in complex delay-coupled SLs networks.

Time-delay signature concealment and physical random bits generation in mutually coupled semiconductor lasers with FBG filtered injection

We propose and demonstrate experimentally the generation of chaos with suppressed time-delay signature (TDS) and physical random bits in two mutually coupled semiconductor lasers (MCSL) by introducing an auxiliary fiber Bragg grating (FBG) filtered injection path. The measurements show that, even by simply adding a single FBG path, the TDS of chaotic signals generated by both lasers in our proposed scheme can be better concealed compared to the conventional MCSL system. Moreover, better TDS concealment can be achieved in the laser with smaller wavelength. Additionally, two random bit streams extracted from the two chaotic lasers in the proposed scheme are achieved with minimal post-processing. The total generation rate reaches 640-Gbps.

Optimizing chaos time-delay signature in two mutually-coupled semiconductor lasers through controlling internal parameters

In this contribution, the effects of two key internal parameters, i.e. the linewidth-enhancement factor [Formula: see text] and gain nonlinearity [Formula: see text], on time-delay signatures (TDS) concealment of two mutually-coupled semiconductor lasers (MCSLs) are numerically investigated. In particular, the influences of [Formula: see text] and [Formula: see text] on the TDS concealment are compared and discussed systematically by setting different values of frequency detuning [Formula: see text] and injection strength [Formula: see text]. The results show that the TDS can be better suppressed with high [Formula: see text] or lower [Formula: see text] in the MCSLs. Two sets of desired optical chaos with TDS being strongly suppressed can be generated simultaneously in a wide injection parameter plane provided that [Formula: see text] and [Formula: see text] are properly chosen, indicating that optimizing TDS suppression through controlling internal parameters can be generalized to any delayed-coupled laser systems.

Suppression of Chaos Time Delay Signature in a Ring Network Consisting of Three Semiconductor Lasers Coupled With Heterogeneous Delays

The properties of chaos time delay signature (TDS) in a ring network consisting of three mutually coupled semiconductor lasers (MCSLs) are investigated numerically, where heterogeneous coupling delays are proposed to obtain the TDS concealment from the intensity chaos in wide parameter regions. The evolution of the TDS patterns, which are quantified via the autocorrelation function, for a ring network with identical coupling delays as well as that with heterogeneous coupling delays is compared. By analyzing the effects of the coupling strength, frequency detuning, and injection current on the TDS, the parameter regions for successful TDS concealment are identified. It is found that the intensity chaos with a desirable TDS concealment can be generated in the proposed ring network in which the TDS is mainly affected by the injection current and coupling strength, but is not so sensitive to the frequency detuning. In particular, a larger injection current and smaller coupling strength are preferable to obtain chaos with a low TDS. Besides, the ring network with heterogeneous coupling delays allows for better TDS concealment in much wider parameter regions, compared to that with identical coupling delays, and, thus, is highly desirable for the chaos-based random bit generators.

Experimental synchrony of semiconductor lasers in coupled networks.

The emission and synchronization of mutually-coupled semiconductor lasers with short cavities has been already recorded, with transversely unstable solutions existing within the chaotic synchronization manifold. Noise and laser-mismatch induced instabilities cause short de-synchronization events within the overall generalized synchronization, influencing the pragmatism of using these signals in secure data exchange applications. However, such operation can be functional for user authentication and sensing applications by assessing a time-averaged performance of synchrony. Until now, this has not been examined either in large-scale laser network configurations or in large transmission coupling paths, as real network implementations oblige. Here we present the first implementation of a fully-coupled fiber network with up to 16 semiconductor lasers, independently controlled and coupled through long interacting cavities. High level of consistent global or cluster synchrony via chaotic signals is demonstrated among all devices of the same origin and under appropriate operation. Devices that are not identical fail to synchronize at any condition, when coupled to the network. Under multiplexed operation, groups of lasers that emit at spectral distances as low as 50pm are shown to preserve intra-cluster synchronization when transmitted in the same fiber-optic channel, despite their large bandwidth of emitted signals.

Tbits/s physical random bit generation based on mutually coupled semiconductor laser chaotic entropy source.

Using two mutually coupled semiconductor lasers (MC-SLs) outputs as chaotic entropy sources, a scheme for generating Tbits/s ultra-fast physical random bit (PRB) is demonstrated and analyzed experimentally. Firstly, two entropy sources originating from two chaotic outputs of MC-SLs are obtained in parallel. Secondly, by adopting multiple optimized post-processing methods, two PRB streams with the generation rate of 0.56 Tbits/s are extracted from the two entropy sources and their randomness are verified by using NIST Special Publication 800-22 statistical tests. Through merging the two sets of 0.56 Tbits/s PRB streams by an interleaving operation, a third set of 1.12 Tbits/s PRB stream, which meets all the quality criteria of NIST statistical tests, can be further acquired. Finally, after additionally taking into account the restriction of the min-entropy, the generation rate of two sets of PRB stream from the two entropy sources can still attain 0.48 Tbits/s, and then a third set of merging PRB stream is 0.96 Tbits/s. Moreover, for the sequence length of the order of 10 Gbits, the statistical bias and serial correlation coefficient of three sets of PRB streams are also analyzed.

Spontaneous exchange of leader-laggard relationship in mutually-coupled semiconductor lasers

Spontaneous exchange of leader-laggard relationship in mutually-coupled semiconductor lasers

Bidirectional chaos synchronization and communication based on mutually coupled semiconductor lasers with asymmetrical bias currents

In this paper, a bidirectional chaos secret communication system, based on mutually coupled semiconductor lasers (MCSLs) with asymmetrical bias currents, is proposed, and the synchronization characteristics and the communication performances of such a system are numerically investigated. The results show that the stable leader-laggard chaos synchronization can be achieved under relatively large asymmetrical bias current levels. Meantime, the influence of the intrinsic parameter variations of the laser on the synchronization quality is also considered, and the simulation reveals that this system still possesses good robustness to the parameter variations. Moreover, the influences of delay time and mutually coupling strength between the two lasers on chaos communication performance have also been discussed. Finally, unidirectional and bidirectional secret communication performances of such a system are examined under the chaos masking (CMS) encryption scheme, and the security of this system is also discussed.

Chaos synchronization in mutually coupled semiconductor lasers with asymmetrical bias currents

We experimentally and numerically investigated the chaos synchronization characteristics of mutually coupled semiconductor lasers (MCSLs) with asymmetrical bias currents. Experimental results show that, asymmetrical bias current level of two MCSLs has obvious influence on chaos synchronization between them, and stable leader-laggard chaos synchronization can be realized under relatively large asymmetrical bias current levels. Moreover, the influences of frequency detuning and mutually coupling strength between the two lasers on chaos synchronization performance have also been discussed. Theoretical simulations basically conform to our experimental observations.

Chaos Synchronization and Communication in Mutually Coupled Semiconductor Lasers Driven by a Third Laser

We numerically investigate the chaos synchronization and message transmission between two mutual coupling semiconductor lasers (MCSLs) subject to identical unidirectional injections (UIs) from an external cavity semiconductor laser (ECSL). The synchronization between the MCSLs is realized through injection locking in conjunction with symmetric operation. The simulation results show that stable isochronal synchronization between the MCSLs can be achieved under proper driving injections. This type of synchronization is robust to parameter mismatch up to tens of percentage and frequency detuning of several tens of gigahertz, which is much better than those of the MCSLs systems with self-feedback. Moreover, the investigations on the mutual chaos pass filtering effects and the message transmission indicate that the isochronal synchronization allows mutual message exchange with a bit rate higher than 10 Gb/s, when the chaos modulation technology is adopted. In addition, the MCSLs can synchronize with the ECSL for proper UI and MC, which provides an opportunity for array chaos synchronization and chaos communication networks. Finally, leader/laggard synchronization can also be achieved in the proposed system.

Multiaccess Optical Chaos Communication Using Mutually Coupled Semiconductor Lasers Subjected to Identical External Injections

A chaos-based communication scheme allowing for multiaccess message transmission is proposed. In this scheme, two mutually coupled semiconductor lasers (MCSLs) are identically driven by an external cavity semiconductor laser (ECSL). The MCSLs isochronally synchronize with each other through symmetric operation, and they laggardly synchronize to the ECSL through injection-locking. When external modulation is adopted, strong chaos pass filtering effects that are not restricted by the relaxation oscillation frequencies of the MCSLs are observed, which enables us to achieve high bit-rate multiaccess chaos communication. Moreover, the security can be improved by making use of the multiaccess ability. This scheme can be used as a rudiment of chaos communication networks.