基于1/4波片的腔增强自发参量下转换过程中双折射效应的补偿  

Birefringence compensation utilizing quarter-wave plates in cavity-enhanced spontaneous parametric down-conversion process

作　　者：贺海 杨鹏飞[1,2] 张鹏飞 李刚[1,2] 张天才[1,2] He Hai;Yang Peng-Fei;Zhang Peng-Fei;Li Gang;Zhang Tian-Cai(State Key Laboratory of Quantum Optics and Quantum Optics Devices,Shanxi University,Taiyuan 030006,China;Collaborative Innovation Center of Extreme Optics,Shanxi University,Taiyuan 030006,China)

机构地区：[1]山西大学,量子光学与光量子器件国家重点实验室,太原030006 [2]山西大学,极端光学省部共建协同创新中心,太原030006

出　　处：《物理学报》2023年第12期123-129,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11974223,11974225);山西省“1331工程”重点学科建设基金资助的课题。

摘　　要：腔增强的光学自发参量下转换是量子光学中产生量子光场的基本方法之一,然而下转换过程往往受到非线性晶体的双折射效应的影响.特别是在利用II类准相位匹配非线性晶体产生双光子对的过程中,晶体的双折射效应使得信号光和闲置光不能同时起振.本文提出并验证了一种利用1/4波片补偿信号光和闲置光的光程的方法,在保证较小内腔损耗及良好的调节自由度的情况下,以相对简洁的装置实现信号光和闲置光的双共振.Single-photon source is an essential element in quantum information processing,and extensively used in the proof-in-principle demonstration in quantum physics,quantum imaging,quantum cryptography,etc.Considering the operating temperature and system complexity,it is a favorable option to choose spontaneous parametric down-conversion(SPDC)combined with the enhancement effect of a cavity.When generating significant single-photon source via the cavity-enhanced type-II spontaneous parametric down-conversion method,there appears inevitable birefringence effect which obviously influences the resonance condition.In order to compensate for birefringence effect,different approaches have been used such as introducing compensating crystal,placing a half-wave plate,tuning the temperature of the nonlinear crystal,customized conjoined double-cavity structure,and cluster effect.In this work,two quarter-wave plates,with an angle of 45°between the optical axis and the crystal axis,are placed in the cavity to ensure the double resonance of signal photon and idler photon.In the process,the signal photon and idler photon generated simultaneously have different polarizations perpendicular to each other through the type-II nonlinear crystal.Considering horizontally polarized photon,its polarization is changed into left circular polarization by the first quarter-wave plate and then returns as vertical polarization.After traversing a long optical path,it shifts to right circular polarization through the second quarter-wave plate.When the photon passes through the same quarter-wave plate again,the polarization state is originally converted into horizontal polarization state.Then the photon completes a round-trip.The other photon with vertical polarization experiences the same process.As a result,the signal photon and idler photon travel identical optical path.The general explanation is described by the Jones matrices,with the emphasis on the transformation of the polarizations of photons.This method can effectively compensate for birefri

关 键 词：腔增强自发参量下转换 双折射效应 双共振 预告式单光子源 

分 类 号：O431.2[机械工程—光学工程]