Chaotic Semiconductor Lasers Research Articles

Chaotic Time-Delay Signature Suppression and Entropy Growth Enhancement Using Frequency-Band Extractor.

By frequency-band extracting, we experimentally and theoretically investigate time-delay signature (TDS) suppression and entropy growth enhancement of a chaotic optical-feedback semiconductor laser under different injection currents and feedback strengths. The TDS and entropy growth are quantified by the peak value of autocorrelation function and the difference of permutation entropy at the feedback delay time. At the optimal extracting bandwidth, the measured TDS is suppressed up to 96% compared to the original chaos, and the entropy growth is higher than the noise-dominated threshold, indicating that the dynamical process is noisy. The effects of extracting bandwidth and radio frequencies on the TDS and entropy growth are also clarified experimentally and theoretically. The experimental results are in good agreements with the theoretical results. The skewness of the laser intensity distribution is effectively improved to 0.001 with the optimal extracting bandwidth. This technique provides a promising tool to extract randomness and prepare desired entropy sources for chaotic secure communication and random number generation.

Experimental Evidence of Chaotic Resonance in Semiconductor Laser

In this paper, an experimental study has been conducted regarding the indication of resonance in chaotic semiconductor laser. Resonant perturbations are effective for harnessing nonlinear oscillators for various applications such as inducing chaos and controlling chaos. Interesting results have been obtained regarding to the effect of the chaotic resonance by adding the frequency on the systems. The frequency changes nonlinear dynamical system through a critical value, there is a transition from a periodic attractor to a strange attractor. The amplitude has a very relevant impact on the system, resulting in an optimal resonance response for appropriate values related to correlation time. The chaotic system becomes regular under a moderate frequencies or amplitudes. These dynamics of the laser output are analyzed by time series, FFT and bifurcation diagram as a result.

面向混沌半导体激光器的高稳定控制系统设计

面向混沌半导体激光器的高稳定控制系统设计

Exploring frequency effects in chaotic semiconductor laser

The issue related to the chaos control in semiconductor laser has drew attention. The resonant perturbations have been of high importance with regard to the harnessing non-linear oscillators for different applications including inducing chaos as well as controlling chaos. Interesting results have been obtained regarding to the effect of the chaotic resonance by adding the frequency on the chaotic systems. The forcing frequency changes nonlinear dynamical system via critical value, there has been transition from periodic attractor to strange attractor. The experimental studying for the evaluation of chaos modulation behavior are considered in the case when frequency related to external perturbation has been changed, whereas the amplitude related to such perturbation has been fixed. This dynamic regarding laser output have been analyzed by time series, the FFT as well as the plot diagram as a result of this data.

Deep Learning-Based Security Verification for a Random Number Generator Using White Chaos.

In this paper, a deep learning (DL)-based predictive analysis is proposed to analyze the security of a non-deterministic random number generator (NRNG) using white chaos. In particular, the temporal pattern attention (TPA)-based DL model is employed to learn and analyze the data from both stages of the NRNG: the output data of a chaotic external-cavity semiconductor laser (ECL) and the final output data of the NRNG. For the ECL stage, the results show that the model successfully detects inherent correlations caused by the time-delay signature. After optical heterodyning of two chaotic ECLs and minimal post-processing are introduced, the model detects no patterns among corresponding data. It demonstrates that the NRNG has the strong resistance against the predictive model. Prior to these works, the powerful predictive capability of the model is investigated and demonstrated by applying it to a random number generator (RNG) using linear congruential algorithm. Our research shows that the DL-based predictive model is expected to provide an efficient supplement for evaluating the security and quality of RNGs.

Simulation of Monolithically Integrated Semiconductor Laser Subject to Random Feedback and Mutual Injection

Aiming at the problems of limited bandwidth and periodicity of chaotic laser, a monolithically integrated chaotic semiconductor laser subject to random feedback and mutual injection is proposed. The chaotic laser consists of two distributed feedback laser diodes (DFB-LD), two semiconductor optical amplifiers (SOA) and a passive optical waveguide. Optical injection of two coupled DFB-LDs achieves chaotic signal shaping and bandwidth enhancement. Random grating along the passive waveguide provides stochastic feedback to suppress the time delay signature (TDS). A theoretical model is established based on the Lang-Kobayashi model to explore the dynamics of the proposed chaotic laser. A chaotic signal with TDS of 0.06 and bandwidth of 13.12 GHz is obtained by simulation. Furthermore, the effects of parameters including feedback ratio, mutual injection ratio, and detuning frequency on the TDS and bandwidth of chaotic signal are investigated. The results show that the broadband chaotic laser signal with TDS suppression can be obtained by controlling parameters reasonably.

Effect of control parameters on chaos synchronization by means of optical feedback

An optical communication scheme based on the synchronization of two chaotic semiconductor lasers is investigated experimentally. Two schemes of optical feedback injection, bidirectional and unidirectional, have been used. Synchronization of the chaos is achieved by coupling a fraction of the transmitter’s output power to the driving current of the receiver. We present experimental results on the different routes of chaos synchronization. First is by using different current densities from master to slave-making synchronization, second is to apply different frequencies with fixed amplitude by using an external perturbation, and third is by applying a different amplitude white noises signals. Our results show that the third route has perfect results of synchronization. The last two routes are new methods and their experimental results are presented for the first time in making chaos synchronization. Finally, the quality of the synchronization was studied by different methods such as a Cross-Correlation Coefficient and Residual Chaos.

Bidirectional communication with time-delay concealment in a system combining all-optical intensity and electrooptical phase chaos

In this paper, we propose and study theoretically a novel architecture, which combines all-optical intensity chaos and electrooptical-phase chaos generator, allows for bidirectional secure communication. The configuration includes three all-optical chaotic semiconductor lasers and two identical phase-chaos electrooptic delayed oscillators in the optic-fiber link. We investigate the complexity degree of this chaotic time trace generated in this system and the concealment of the time delay signature (TDS), and systematically analyze the influence of the parameter mismatch on synchronization performance , We demonstrate that the system can generate the chaos with high complexity degree through a calculation of the largest Lyapunov exponent (LLE), Lempel–Ziv complexity (LZC), permutation entropy (PE) and fractal box-counting dimension (FBCD); the TDS of an electro-optical delayed oscillator is concealed by calculating the autocorrelation function (ACF) and the delayed mutual information (DMI); the parameter mismatches, such as the TDS, the bias current, the line width enhancement factor (LWEF), etc., have the influence on the synchronization performance; the changes of the bit rate and the modulation index have the influence on Q-factor of the system. Moreover, our numerical simulations also reveal that, under the parameter match condition the delayed chaotic dynamics can be identically synchronized and the synchronization solution is robust. At last, we successfully achieve the simultaneously bidirectional exchange of the messages introduced on the two sides of a link.

三种混沌半导体激光系统的延时特性和有效带宽分析

三种混沌半导体激光系统的延时特性和有效带宽分析

光子集成混沌半导体激光器研究进展（特邀）

光子集成混沌半导体激光器研究进展（特邀）

光子集成混沌半导体激光器研究进展（特邀）

光子集成混沌半导体激光器研究进展（特邀）

Precise Photon Correlation Measurement of a Chaotic Laser

The second order photon correlation g(2)(τ) of a chaotic optical-feedback semiconductor laser is precisely measured using a Hanbury Brown–Twiss interferometer. The accurate g(2)(τ) with non-zero delay time is obtained experimentally from the photon pair time interval distribution through a ninth-order self-convolution correction. The experimental results agree well with the theoretical analysis. The relative error of g(2)(τ) is no more than 5‰ within 50 ns delay time. The bunching effect and coherence time of the chaotic laser are measured via the precise photon correlation technique. This technique provides a new tool to improve the accuracy of g(2)(τ) measurement and boost applications of quantum statistics and correlation.

Permutation entropy analysis of chaotic semiconductor laser with chirped FBG feedback

We numerically analyze the chaos complexity of a semiconductor laser with chirped fiber Bragg grating (CFBG) feedback by utilizing the permutation entropy (PE). Due to dispersion-induced nonlinearity of chirped grating, the time delay signature (TDS) can be suppressed or erased and the complexity enhancement is expected. The effects of laser parameters on PE as well as the TDS are studied in detail. The results show that for CFBG feedback, the TDS can be suppressed in the range of parameters where linewidth enhancement factor exceeds 3 and gain saturation coefficient is lower than 4×10−4μm3, and the complexity of chaotic signals is enhanced. As the feedback strength and bias current increase, the PE value under CFBG feedback increases linearly to a maximum of 0.994 and remains stable. Compared with mirror feedback, CFBG feedback can achieve increased complexity over a wider range of parameters. In addition, when the dispersion value of the chirped grating exceeds 2000 ps/nm, the frequency detuning range of -15 GHz to 10 GHz is beneficial to obtain chaotic signals with higher PE values.

Long-Range and High-Precision Fault Measurement Based on Hybrid Integrated Chaotic Laser

We propose a long-range, high-precision optical time domain reflectometry (OTDR) technology based on the hybrid integrated short-external-cavity chaotic semiconductor laser (SCSL) which has the advantages of small volume, simple process, low cost, mass production, stable performance, and high yield. The chaotic signal generated by the hybrid integrated SCSL exhibits a certain extent of oscillations and fluctuates randomly in time series. It can be seen from the auto-correlation curve that the generated chaotic signal has no time-delay signature and the theoretical spatial resolution is 1 cm according to the full width of half maximum. In this letter, not only the measurement of multiple single reflection events but also the measurement of double-reflection events was realized, and the spatial resolutions at different distances were verified. Finally, the spatial resolution and range-independent breakpoints measurement has been realized, and the detection range of 76.54 km and the spatial resolution of 1 cm (7.7 million resolved points) have been experimentally demonstrated.

Experimental evidence of Phase Control method in chaotic Semiconductor Laser

we study how to control the dynamics of excitable systems by using the phase control technique.We study how to control nonlinear semiconductor laser dynamics with optoelectronic feedback using the phase control method. The phase control method uses the phase difference between a small.added frequenc y and the main driving frequency to suppress chaos, which leads to various periodic orbits. The experimental studying for the evaluation of chaos modulation behavior are considered in two conditions, the first condition, when one frequency of the external perturbation is varied, secondly, when two of these perturbations are changed. The chaotic system becomes regular under one frequency or two frequencies, But in two frequencies, phase control showed an excellent ability to maintain regular behavior in chaotic window and reexcite chaotic behavior when destroyed. This dynamics of the laser output are analyzed by time series and bifurcation diagram.

Multi-user image encryption algorithm based on synchronized random bits generator in semiconductor lasers network

A chaos-based public channel image encryption algorithm among three users is proposed, where the random bits (RBs) generated in a star-type chaotic laser network can be well synchronized and are used as the keys. The proposed algorithm is simple and efficient. Firstly, random bits with verified randomness are generated from the synchronized chaotic semiconductor lasers in a star-type network at a rate of 10Gb/s. Next, lower-triangular error-bits detection is employed to delete the different bits among all the parties over the public channel. Based on the synchronized RBs, the XOR operation is used to diffuse the plain image. Then the hash algorithm is used to get the control parameters matrix from the plain image, and 3D cat map is used to confuse the pixel position through the parameters matrix. Finally, the encrypted image is transmitted in the public channel. The performance tests results, such as key sensitivity, histogram, correlation, differential attack, robustness and entropy analysis, show that the suggested algorithm prevents a powerful computational eavesdropper. Besides, the running speed of this algorithm is linear with the size of plain image. These results open possibilities for multi-user secure communication application.

2.24-Tb/s Physical Random Bit Generation With Minimal Post-Processing Based on Chaotic Semiconductor Lasers Network

Multi-channel physical random bit generator (RBG) based on a chaotic semiconductor lasers (SLs) network is proposed and experimentally demonstrated. In experiments, a small ring network consisting of three SLs mutually coupled with heterogeneous delays is constructed to obtain chaotic temporal waveforms. The results show that the time-delay signature of chaotic intensities in all the three SLs can be well concealed over wide range of parameters. Through linear combination of the three chaotic outputs, seven channels of chaotic entropy sources can be obtained. Furthermore, by introducing a minimal post-processing technique and directly extracting four least significant bits at 80-GS/s sampling rate, seven channel random bit sequences with verified randomness can be simultaneously achieved, and the total bit rate is 2.24 Tb/s. The proposed RBGs enabling such high generation rate have potential applications in the one-time pad encryption for the high-speed optical communication networks.

Observation of flattened power spectrum of chaotic semiconductor laser using an optical filter

The authors experimentally demonstrate that the spectral flatness of chaotic light from an external-cavity feedback semiconductor laser is significantly improved using a fibre Bragg grating. The effects of detuning between the Bragg frequency and chaotic frequency on the bandwidth and spectral flatness are both investigated. The flatness of the power spectrum is enhanced to ±1.4 dB whilst maintaining the spectral bandwidth at around 8 GHz. The experimental results are in accordance with theoretical predictions which also have shown that the spectral flatness decreases initially then increases with increasing the 3 dB bandwidth of grating. A flattened spectrum with a low-pass energy distribution increases the utilisation efficiency of chaotic light in chaotic radar and reflectometry.

Semiconductor-laser-based hybrid chaos source and its application in secure key distribution.

An analog-digital hybrid optical chaos source and a corresponding secure key distribution (SKD) scheme are proposed. An analog-digital hybrid electro-optic feedback loop is introduced to enhance the robustness of the chaotic semiconductor lasers. The source, which can adopt robust digital synchronization strategies, could generate a broadband analog optical chaotic signal of high dynamical complexity. Furthermore, the source reduces the requirement on the processing speed of digital components and simplifies the hybrid system structure markedly. For demonstrating, we build a SKD system with the proposed chaos source. Since this SKD scheme is compatible with digital optical networks, the commercially available communication techniques can help to make it insensitive to impairments in fiber optic links. This feature has potential in long-haul SKD.

Investigation of the Effect of Intra-Cavity Propagation Delay in Secure Optical Communication Using Chaotic Semiconductor Lasers

The influence of intra-cavity propagation delay in message encoding and decoding using chaotic semiconductor lasers is numerically investigated. A message is encoded at the transmitter laser by a chaos shift keying scheme and is decoded at the receiver by comparing its output with the transmitter laser. The requisite intra-cavity propagation delay in achieving synchronization of optical chaos is estimated by cross-correlation analysis between the transmitter and receiver lasers’ output. The effect of intra-cavity propagation delay on the message recovery has been analyzed from the bit error rate performance. It is found that despite the intra-cavity propagation delay magnitude being less, it has an impact on the quality of message recovery. We also examine the dependency of injection rate, frequency detuning, modulation depth and bit rate on intra-cavity propagation delay and associated message recovery quality. We found that the communication performance has been adequately improved after incorporating intra-cavity propagation delay correction in the synchronization system.