基于外光注入互耦合垂直腔面发射激光器的混沌随机特性研究∗

摘要

In this paper, a randomness-enhanced chaotic system model of mutually coupled vertical-cavity surface-emitting lasers (VCSELs) is established by adding anothor injected VCSEL with variable polarizer optical feedback (VPOF). The randomness of chaotic signals is evaluated quantitatively by an information-theory-based quantifier, the permutation entropy (PE). The influences of VPOF-VCSEL rotating polarizer degree, feedback strength, injection strength, mutual coupling strength, path time delay and frequency detuning about injected VCSEL and coupled VCSELs on chaotic signal permutation entropy are numerically studied. It is shown that the chaotic signal permutation entropy of mutually coupled VCSEL system driven by the third VCSEL is much higher than the mutual system with no-driving VCSEL. That is to say, the randomness of coupled system chaotic signal can be enhanced by optical injection. When the rotating polarizer degree is approximately 45 degrees and the injection strength is saturated at a constant level, the system PE can be increased by coupled strength, which is set to be higher than feedback strength. In addition, unequal delay time between both coupled time and feedback time, and higher detuning frequency between driving VCSEL and coupled VCSELs can contribute to randomness-enhanced chaotic signals.%通过在互耦合垂直腔面发射激光器(VCSELs)系统中增加外光注入，建立了一种基于偏振可调光反馈VCSEL驱动互耦合VCSELs混沌系统模型，分析了增加外光驱动对互耦合激光器随机特性的影响。以不可预测度作为随机特性的评价指标，采用信息论中的排列熵作为相应量化工具，对系统输出混沌信号的不可预测性进行定量分析。数值研究了光强度、时延、偏振旋转角度以及驱动激光器与耦合激光器间的频率失谐对输出信号随机特性的影响。结果表明：外光注入能够增大互耦合VCSELs输出混沌信号的排列熵，即外光注入能够有效提高耦合系统的随机特性；驱动激光器可调偏振片偏转角度调节到45◦附近，注入强度适中，满足耦合强度大于驱动激光器自反馈强度条件，系统输出信号的排列熵较大；在耦合时延与驱动激光器反馈时延不相等的同时，增加驱动激光器与耦合激光器频率失谐，外光注入互耦合VCSELs的随机特性能够得到进一步提高。