基于波长到时间映射快速测量纠缠光子相位匹配波长的实验方法  

Experimental Method for Fast Measuring the Phase-matched Wavelengths of Entangled Photons by Wavelength-to-Time Mapping

作　　者：李百宏[1,2] 夏志广 项晓[2,3] 靳亚晴 权润爱 董瑞芳[2,3] 刘涛 张首刚[2,3] Li Baihong;Xia Zhiguang;Xiang Xiao;Jin Yaqing;Quan Run'ai;Dong Ruifang;Liu Tao;Zhang Shougang(College of Sciences,Xi'an University of Science and Technology,Xi'an,Shaanxi 710054,China;Key Laboratory of Time and Frequency Primary Standards,National Time Service Center,Chinese Academy of Sciences,Xi'an,Shaanxci 710600,China;School of Astronomy and Space Science,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]西安科技大学理学院,陕西西安710054 [2]中国科学院国家授时中心中国科学院时间频率基准重点实验室,陕西西安710600 [3]中国科学院大学天文与空间科学学院,北京100049

出　　处：《中国激光》2021年第3期148-155,共8页Chinese Journal of Lasers

基　　金：国家自然科学基金(12074309,12033007,61801458,61875205,91836301);中国科学院前沿科学重点研究计划(QYZDB-SSW-SLH007);中国科学院战略性先导科技C类专项(XDC07020200);中国科学院重点部署项目(ZDRW-KT-2019-1-0103);广东省重点领域研发计划(2018B030325001);中国科学院“西部之光”B类计划(XAB2019B17,XAB2019B15);陕西省自然科学基础研究计划项目(2019JM-346);西安科技大学优秀青年基金(2019YQ2-13);西安科技大学博士后启动基金(6310121501)。

摘　　要：准相位匹配有利于实现高效的自发参量下转换,它由非线性晶体的极化周期和依赖于温度的折射率决定。为了确定特定波长处所需的晶体温度,需要测量相位匹配波长随晶体温度的变化关系。单色仪的传统测量方法具有测量精度较低且耗时长等缺点。提出了一种实验方法,该方法能快速准确测量纠缠光子相位匹配波长随晶体温度变化的关系。在信号和闲置光路中先后加入色散元件,通过测量纠缠光子对到达时间关联峰值处的时间延迟随晶体温度的变化关系,利用波长到时间的映射关系将其转化为波长随晶体温度的变化关系。给出了周期极化铌酸锂(PPLN)波导和周期极化磷酸氧钛钾(PPKTP)晶体的实验测量结果,测量精度优于0.1 nm,测量时间约为几分钟。测量精度受限于单光子探测器的抖动时间和色散元件色散量的大小。原则上,抖动时间越小,色散量越大,测量精度越高。最后讨论了Sellmeier方程计算的结果与实验结果存在差异的可能原因。所提方法可以用来校准相位匹配波长与晶体温度的关系及极化周期,并有望实现温度依赖的Sellmeier方程的修正或改进。Objective The entangled photons generated by the spontaneous parameter down-conversion(SPDC) process have wide applications in quantum precision measurement,quantum spectroscopy,quantum imaging,quantum teleportation,and quantum security communications.However,one can only obtain a highly efficient SPDC when the phase-matching condition(conservation of momentum) is satisfied.In general,only a few birefringent crystals can meet the phase-matching condition,however the phase-matched wavelength(PMW) and bandwidth of entangled photons are limited.Afterwards,the quasi-phase matching(QPM) technology is proposed to solve the limitation problem of a birefringent crystal by artificially modulating the polling periods of the crystal.QPM is determined by the polling period and the refractive index of the crystal.The crystal temperature can be used to adjust the refractive index and different crystal temperatures are corresponding to different PMWs.To determine the crystal temperature at the required PMW,it is necessary to know the relationship between the PMW and crystal temperature.The temperature-dependent Sellmeier equation can be used to estimate this relationship.However,the Sellmeier equations of many nonlinear crystals are still unknown.Even if the Sellmeier equation is known,there is still a discrepancy between the estimated result and the experimental result in some special wavelengths and temperature ranges since the coefficients in the Sellmeier equation come from some empirical values.Thus,it needs to be revised or improved continuously.Therefore,it is necessary to use some experimental methods to accurately measure the PMW of the entangled photons in the SPDC process.In experiments,a monochromator is usually used to measure the spectrum of entangled photons and thus the relationship between the PMW and the crystal temperature is obtained.However,owing to the scanning for different wavelengths at different crystal temperatures,the measurement is low-accuracy and time-consuming,especially for the entangled broadba

关 键 词：量子光学 纠缠光子 相位匹配波长 晶体温度 波长到时间映射 

分 类 号：O431.2[机械工程—光学工程]