Unpredictability-enhanced Broadband Chaotic Signal Generation Based On VCSEL Subject To Dual Chaotic Optical Injection

In recent years,chaotic signal based on semiconductor laser has been widely used in fields of secure optical communication,high speed random bit generation and chaotic radar.With the rapid development of information society,the bandwidth and unpredictability of chaotic signal are required in the above fields.Previous studies have shown that semiconductor laser are perturbed by dual optical injection to improve the bandwidth and enhance the degree of unpredictability of chaotic signal.Compared with conventional edge-emitting lasers(EEL),vertical-cavity surface-emitting lasers(VCSEL)have the advantages of low threshold current,high coupling rate and easy integration.In particular,VCSEL may simultaneously output two chaotic signals with appropriate external perturbations.Therefore,investigating an unpredictability-enhanced broadband chaotic signal generation based on VCSEL with dual chaotic optical injection is significant.Based on the spin-flip model(SFM),the characteristic of chaotic signals output from 850nm-VCSEL driven by dual chaotic optical injection are theoretically investigated.In order to obtain the chaotic signal with high degree of unpredictability,the injected dual chaotic signals are generated by VCSEL with double optical feedback.The results show that the chaotic signal output by the master lasers(M1-VCSEL and M2-VCSEL)with double optical feedback perturbation have weak time delay signature(TDS)and high degree of unpredictability.When the chaotic signals of M1-VCSEL and M2-VCSEL are injected into S-VCSEL,the bandwidth of chaos output from S-VCSEL is greatly improved,and the degree of unpredictability of chaos is further enhanced.In addition,the effects of the injection strength and frequency detuning of M1-VCSEL and M2-VCSEL on the effective bandwidth and time delay signature peaks of S-VCSEL output were analyzed,and the injection parameter range of S-VCSEL output chaotic signals with high degree of unpredictability and wide bandwidth was obtained.In this paper,self-correlation function(SF)and permutation entropy function(PE)are used to quantify the degree of unpredictability of chaotic signal,and effective bandwidth(EBW)is used to quantify the chaotic bandwidth.