混沌激光光子互相关的分析与测量

Analysis and Measurement of Photon Cross-Correlation of Chaotic Laser

利用非平衡光纤干涉系统,理论分析且实验测量了光反馈强度变化过程中,光场不同状态即相干光、相干与混沌的混合光及混沌光的光子互相关,并实现了对上述光场的区分。研究分析了不同状态光场的二阶光子互相关随着延迟时间和相干时间的变化,结果表明:相干光的二阶光子互相关g^((2x))(τ)只在零延迟处存在极小值且为0.5;混沌光g^((2x))(τ)只在对称延迟处存在两个极大的峰值且为1.25;相干与混沌的混合光g^((2x))(τ)不仅在零延迟处存在极小值,而且在对称延迟处存在两个极大的峰值,同时随着混沌光所占比例的增大,g^((2x))(τ)延迟对称处的峰值从1增至1.25,零延迟处的g^((2x))(0)由0.5增至1,表明此时混合光场正由相干光向混沌光过渡。实验上测量了无反馈时,相干光的二阶光子互相关g^((2x))(τ)并获得光场的相干时间为65 ns;反馈强度在2.5%时,测得混沌激光的g^((2x))(τ)并得出混沌光占比75%,及相应的相干时间0.7 ns;反馈强度为18%时,测得相干塌陷混沌光的g^((2x))(τ)及其相干时间0.8 ns。理论与实验结果符合良好。表明该方法可明确区分不同混沌占比状态下的光场及对应的相干时间,为进一步揭示及监测输出光场的量子统计特性提供了理论和实验基础。

The photon cross-correlations of different light fields,namely coherent light,mixed coherent and chaotic light,and chaotic light,in a changing process of light feedback intensity are investigated theoretically and experimentally via an unbalanced fiber interferometer,and the above-mentioned light fields are distinguished.The second-order photon cross-correlations of the light fields are analyzed as functions of delay time and coherence time.The results show that the second-order photon cross-correlation g^((2x))(τ) of coherent light only has a minimum value of 0.5 at zero delay time.The g^((2x))(τ) of chaotic light has two maximum peaks of 1.25 at symmetric delay time.The g^((2x))(τ) of mixed coherent and chaotic light not only has a minimum value at zero delay time but also has two maximum peaks at symmetric delay time.Meanwhile,as the proportion of chaotic light increases,the peak values of g^((2x))(τ) at symmetry delay time rise from 1 to 1.25 and the g^((2x))(0) at zero delay time increases from 0.5 to 1,indicating that the mixed light is transiting from coherent light to chaotic light.The g^((2x))(τ) of coherent light is measured experimentally under no light feedback,and the corresponding coherent time obtained is 65 ns.When the feedback intensity is 2.5%,the g^((2x))(τ) of the chaotic laser is measured.The proportion of chaotic light is 75%,and the corresponding coherent time is 0.7 ns.When the feedback intensity is 18%,the g^((2x))(τ) of chaotic laser in coherence collapse regime is measured,and its coherent time is 0.8 ns.The experimental results are in good agreement with the theoretical ones.It indicates that this method can clearly distinguish light fields with different proportions of chaotic light and their corresponding coherent time and thereby provide a theoretical and experimental basis for further revealing and monitoring the quantum statistics of output light fields.