摘要
混沌光的延时特征(TDS)和带宽(BW)是影响混沌激光应用的两个重要参量,常用来表征混沌光的混沌特性。将具有外腔光反馈的半导体激光器(SL)作为主激光器,将具有相位调制光反馈的SL作为从激光器,并将主激光器输出的混沌光单向双路注入到从激光器中,构成具有外光单向双路注入的相位调制光反馈的SL系统。数值研究了外光注入系数和反馈系数等参数对系统输出混沌光TDS的影响,进而在TDS被有效抑制的参数条件下,对系统输出混沌光的带宽进行了研究。结果表明,用该方案和通过对参数值区间的适当选取可以有效地抑制混沌激光的TDS,并且混沌激光的3 dB带宽最大约为20 GHz。
Objective As classB lasers,distributed feedback semiconductor lasers(DFBSLs)can output chaotic laser under external disturbances,such as external optical injection and optoelectronic feedback,and the bandwidth is up to GHz.Therefore,DFBSLs are widely applied in many fields,such as secure communication and physical entropy sources for generating random physical numbers.However,the chaotic laser output from DFBSLs has weak periodicity and timedelay signature(TDS)due to optical feedback and optical injection.This would reduce the quality of the random numbers generated with chaotic laser sources and restrict the applications of chaotic laser.In addition,the bandwidth(BW)of the chaotic laser determines the transmission rate of secure communication.For the above reasons,the TDS and BW are two important parameters that affect chaotic laser's applications and are often used to characterize the chaotic characteristics of chaotic laser.This paper presents a semiconductor laser system with external unidirectional dualpath optical injection and phasemodulated optical feedback(SLEUDOIPMOF)and investigates its effectiveness in suppressing the TDS and broadening the BW of chaotic laser.The results of this paper are significant for achieving information confidentiality and highspeed transmission in chaotic laserbased secure communication.Methods This paper presents a scheme of semiconductor lasers.Specifically,a DFBSL with an externalcavity optical feedback is used as the master laser,while a DFBSL with the PMOF is taken as the slave laser.Subsequently,the chaotic laser output from the master laser is injected into the slave laser through two paths.The SLEUDOIPMOF is thereby obtained.Then,the influences of parameters,including the external optical injection coefficients and the feedback coefficients,on the TDS of the chaotic laser output from the SLEUDOIPMOF are numerically investigated.The timedelay eigenvalueβis defined as the maximum value of the timedelay eigenpeaks in the autocorrelation function curve of the chaotic laser.Whenβ<0.2,the TDS is suppressed.Furthermore,the BW of the chaotic laser is examined under the parameters enabling effective suppression of the TDS.Results and Discussions Regarding the SLEUDOIPMOF proposed in this paper,the external optical feedback cavity for the slave laser contains a phase modulator driven by pseudorandom signals,and this would conceal the timedelay eigenpeaks and the TDS generated by the timedelay information of the injected laser and the feedback laser.Thus,the TDS is effectively suppressed.The numerical results show that the TDS of the chaotic laser output from the system is effectively suppressed by optimizing parameter values in the selected parameter value ranges,namely,the timedelay eigenvalueβis smaller than 0.2[Fig.2(b)and Figs.3-7].Besides,the minimum value ofβis close to 0.06(Fig.4 and Figs.6-7).In the proposed SLEUDOIPMOF,an external optical feedback cavity is equipped for the master laser,and chaotic laser can thus be output and further injected into the slave laser through two paths.The interference between the injected chaotic laser in the two paths enlarges the intensity of the laser injected into the slave laser,ultimately broadening the BW of the chaotic laser output from the slave laser.The numerical results reveal that the BW is effectively widened under the parameters enabling effective suppression of the TDS,and the maximum value of the 3-dB BW of the chaotic laser obtained is about 20 GHz[Fig.9(c2)and Fig.10].Conclusions This paper proposes the SLEUDOIPMOF system for suppressing the TDS and broadening the BW of chaotic laser.For this purpose,the influences of the system's parameters on the TDS are numerically investigated,and the results are physically analyzed.The results show that in the selected parameter value ranges,the timedelay eigenvalueβdecreases first and then increases as the feedback coefficient K m or the pumping factor of the master laser increases.The value ofβdecreases as the feedback coefficient Ks or the two injection coefficients increase.Moreover,the value ofβincreases first and then decreases with an increasing frequency detuning,and it decreases first,then varies in a gentle manner,and rises slightly higher afterwards with the increase in the pumping factor of the slave laser.The optimal parameter value ranges for suppressing the TDS effectively are obtained accordingly.Then,the BW is investigated under the parameters enabling effective suppression of the TDS,and the result is physically analyzed.The analysis results show that the value of the BW increases rapidly first and then decreases slowly as the feedback coefficient K m or the pumping factor of the slave laser increases.It increases with an increasing injection coefficient K2 or an increasing feedback coefficient Ks.The value of the BW increases first and then varies gently as the pumping factor of the master laser rises,and it increases gradually first and then decreases rapidly with an increasing frequency detuning.The maximum value of the 3-dB BW of the chaotic laser obtained is about 20 GHz.
作者
庞爽
冯玉玲
于萍
Pang Shuang;Feng Yuling;Yu Ping(Department of Physics,Changchun University of Science and Technology,Changchun 130022,Jilin,China)
出处
《光学学报》
EI
CAS
CSCD
北大核心
2023年第3期156-165,共10页
Acta Optica Sinica
基金
吉林省科技发展计划(201902011135JC)。
关键词
激光器
分布反馈半导体激光器
混沌激光
相位调制光反馈
延时特征
带宽
lasers
distributed feedback semiconductor laser
chaotic laser
phasemodulated optical feedback
timedelay signature
bandwidth
