Generation Of Multi-channel High-quality Chaotic Signals Based On A Ring System Composed Of Polarization Rotated Coupled 1550nm VCSELs

In recent years,with the rapid development of information technology,chaotic laser signal generated by the semiconductor laser(SL)has become a focus due to its great application prospects such as high-speed secure optical communication,chaotic radar and high-speed random number generation,etc.In general,SL subject to different external perturbations such as optical feedback,optical injection or optoelectronic feedback can generate chaotic signals.Among these,an obvious time delay signature(TDS)can be observed in the chaotic signal generated by SL subject to optical feedback,which can hinder the applications of chaotic laser signal in the fields of secure optical communication and random number.Consequently,it is necessary to suppress the TDS of chaotic signals.Especially,vertical-cavity surface-emitting lasers(VCSELs)can simultaneously have two orthogonal polarization components(X-PC,Y-PC)under suitable conditions.As for a ring system composed of three or more VCSELs,it can theoretically produce multi-channel chaotic laser signals.Moreover,multi-channel random bit sequences can be generated once above-mentioned ring system is used as a chaotic entropy source.In this paper,a scheme generating multi-channel high-quality chaotic signals based on a ring system composed of three unidirectionally polarization-rotated coupled 1550nm-VCSELs is proposed.Adopting the spin flip model,the polarization-resolved dynamical characteristics of the three VCSELs in the ring system are theoretically investigated.Using self-correlation function(SF)and mutual information(MI),the TDS of the polarization-resolved chaotic signal output from these VCSELs is analyzed.Moreover,the cross-correlations between different polarization components are also discussed.The results show that the 1550 nm VCSEL can simultaneously lase two orthogonal polarization components with comparative output powers by adjusting the injection intensity and frequency detuning.Under the appropriate injection intensity and frequency detuning,the six polarization components of three 1550nm-VCSELs can exist simultaneously.The injection intensity and frequency detuning have a significant effect on the TDS of each chaotic signal from these VCSELs.For fixed injection intensity or frequency detuning,the delay signature peaks of these chaotic outputs can be all suppressed below 0.2.Combined of the influence of injection intensity and frequency detuning on TDS suppression,the region of coupled parameters for generating sixchannel chaotic signals with weak TDS can be obtained.After taking into account the cross-correlation among the six-channel chaotic signal outputs,an optimized parameter region with weak cross-correlation between two signals from different VCSELs can be determined.As a result,the ring system can simultaneously generate six-channel chaotic laser signals with suppressed TDS,while the cross-correlation between two signals from different VCSELs is weak.