[论文解读] Spectral and statistical properties of high-gain parametric down-conversion

Kirill Yu. Spasibko|arXiv (Cornell University)|Jul 25, 2020

Advanced Fiber Laser Technologies参考文献 155被引用 4

一句话总结

本论文研究了高增益参量下转换（PDC）作为明亮压缩真空（BSV）态的光源，其具有强烈的非经典特性和统计特性。结果表明，高增益PDC可产生宏观亮度高、正交压缩的光场，其光子数分布具有重尾特征，与相干光相比，可将多光子过程（如谐波生成）的效率提升达两个数量级，从而为超快光谱学和量子增强成像等新应用提供可能。

ABSTRACT

Parametric down-conversion (PDC) is mostly known in the low-gain (spontaneous) regime, in which the correlated photon pairs are produced. Spontaneous PDC (SPDC) plays a very important role for quantum optics as a variety of quantum states is produced via SPDC. In the high-gain case PDC leads to generation of bright states having up to hundreds mW mean power. With such states almost any nonlinear optical interaction or light-matter interaction becomes more efficient. Even being macroscopically bright, the produced states maintain nonclassical properties as, for example, the fluctuations of electric field quadratures are squeezed below the shot-noise level. The high-gain PDC could be used not only in the same applications as SPDC, it also can provide new ones. Apart from that the high-gain PDC has many remarkable spectral and statistical properties, which are in the focus of this work. The description starts from the PDC generation in normal and anomalous group velocity dispersion ranges. The spectrum and mode content of high-gain PDC is considered as well as their change with the parametric gain are demonstrated. Then, there are the interference effects emerging from the PDC correlations presented, namely the macroscopic analogue of the Hong-Ou-Mandel interference. In addition, it is shown how spatial and temporal walk-off matching could be used for the generation of giant narrowband twin beams. Finally, the statistical properties of high-gain PDC are reviewed as well as their use for multiphoton effects is demonstrated. Photon-number fluctuations of PDC are studied via normalized correlation functions and probability distributions. These fluctuations enhance the generation efficiency for multiphoton effects by orders of magnitude and lead to tremendously fluctuating light described by heavy-tailed photon-number probability distributions.

研究动机与目标

• 研究高增益参量下转换（PDC）在传统低增益区域之外的光谱与统计特性。
• 理解高参量增益如何导致宏观亮度高、非经典的光场，其光子数涨落强烈。
• 展示高增益PDC作为多光子过程泵浦源的应用，显著提升效率。
• 探索由巨大孪生光束和重尾光子数分布所开启的新应用。
• 建立实验与理论框架，用于表征高增益PDC中的光谱关联、模式成分及干涉效应。

提出的方法

• 在正常和异常群速度色散（GVD）区域对PDC进行理论建模，以分析其光谱与模式结构。
• 通过窄带滤波和强度差噪声分析，实验测量联合光谱强度（JSI）和相关函数（CF）。
• 在非线性晶体中利用时间与空间走离匹配技术，生成窄带、高增益孪生光束。
• 应用归一化相关函数与互补累积分布函数（CCDF）以表征光子数涨落。
• 实施分束器干涉实验，观测高增益PDC中的宏观Hong-Ou-Mandel（HOM）效应。
• 展示从BSV产生的二次、三次和四次谐波生成，与相干光泵浦进行效率对比。

实验结果

研究问题

• RQ1 在异常GVD区域，随着参量增益增加，高增益PDC的光谱与模式特性如何演化？
• RQ2 在高增益PDC中，干涉效应（如宏观HOM干涉）的本质是什么？
• RQ3 在明亮压缩真空（BSV）中，光子数涨落对多光子过程（如谐波生成）的增强程度如何？
• RQ4 如何利用时空走离匹配在高增益PDC中生成巨大、窄带孪生光束？
• RQ5 在高增益PDC中，哪些统计特性（如重尾光子数分布）出现，它们如何影响非线性过程？

主要发现

• 高增益PDC可产生平均功率达数百毫瓦的明亮压缩真空（BSV）态，同时保持低于散粒噪声的正交分量涨落。
• BSV的归一化相关函数在窄带滤波下保持不变，证实了非经典关联的鲁棒性。
• 当以BSV作为泵浦源时，二次、三次和四次谐波生成等多光子过程的效率相比相干光泵浦可提升达两个数量级。
• BSV中极端的光子数涨落导致重尾概率分布，频繁观测到光子数超过平均值100倍以上的事件。
• 从BSV产生的超连续谱具有幂律光子数分布，指数小于2，导致平均光子数未定义，统计特性呈现重尾特征。
• 实验观测到宏观Hong-Ou-Mandel干涉，证明了高增益PDC系统中集体量子行为的存在。